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Multiparous mothers have greater umbilical blood flow and thus more efficient transport of pollutants than primiparous mothers. We tested a hypothesis that multiparous mothers are more prone to have an infant with low birth weight (LBW) after prenatal exposure to air pollution. A study was conducted on a representative group of more than 74,000 singleton, live, full-term infants. Birth data were obtained from the birth registry, while pollution data were from an environmental monitoring system (Poland). Multiple comparisons were controlled by the false discovery rate procedure (FDR). After standardization, the harmful effect of carbon monoxide (CO) on the odds ratio (OR) for LBW was seen among the multiparous mothers (OR = 1.28; 95% CI 1.06–1.54), while in primiparous mothers it was nonsignificant. The effect of CO on the OR for LBW differed according to parity, which was confirmed by the test for interaction (FDR-adjusted p = 0.03). The interaction between parity and sulfur dioxide (SO2) was statistically nonsignificant (FDR-adjusted p = 0.08). Multiparous mothers may be more vulnerable to CO than primiparous mothers. Parity may be the modifier of the association between pollutants and the risk of LBW.
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Biodemography and Social Biology
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Parity Conditions the Risk for Low Birth Weight
after Maternal Exposure to Air Pollution
Anna Merklinger-Gruchala, Grazyna Jasienska & Maria Kapiszewska
To cite this article: Anna Merklinger-Gruchala, Grazyna Jasienska & Maria Kapiszewska
(2017) Parity Conditions the Risk for Low Birth Weight after Maternal Exposure to Air Pollution,
Biodemography and Social Biology, 63:1, 71-86, DOI: 10.1080/19485565.2016.1264872
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Published online: 13 Mar 2017.
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Parity Conditions the Risk for Low Birth Weight after Maternal
Exposure to Air Pollution
Anna Merklinger-Gruchala
, Grazyna Jasienska
and Maria Kapiszewska
Department of Pediatrics, Faculty of Medicine, Andrzej Frycz Modrzewski Krakow University, Krakow, Poland;
Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University Medical College,
Krakow, Poland;
Department of Health and Medical Sciences, Andrzej Frycz Modrzewski Krakow University,
Krakow, Poland
Multiparous mothers have greater umbilical blood ow and thus more
ecient transport of pollutants than primiparous mothers. We tested a
hypothesis that multiparous mothers are more prone to have an infant
with low birth weight (LBW) after prenatal exposure to air pollution. A
study was conducted on a representative group of more than 74,000
singleton, live, full-term infants. Birth data were obtained from the birth
registry, while pollution data were from an environmental monitoring
system (Poland). Multiple comparisons were controlled by the false
discovery rate procedure (FDR). After standardization, the harmful eect
of carbon monoxide (CO) on the odds ratio (OR) for LBW was seen
among the multiparous mothers (OR = 1.28; 95% CI 1.061.54), while
in primiparous mothers itwas nonsignicant. The eect of CO on the OR
for LBW diered according to parity, which was conrmed by the test for
interaction (FDR-adjusted p= 0.03). The interaction between parity and
sulfur dioxide (SO
) was statistically nonsignicant (FDR-adjusted
p= 0.08). Multiparous mothers may be more vulnerable to CO than
primiparous mothers. Parity may be the modier of the association
between pollutants and the risk of LBW.
A large body of literature has documented the association between atmospheric pollution
and human reproduction (Woodruet al. 2010). In particular, female reproductive
physiology is sensitive to perceived environmental conditions, including lifestyle
(Jasienska et al. 2006; Kapiszewska et al. 2006; Merklinger-Gruchala et al. 2008;
Ziomkiewicz et al. 2008) and air pollution (Tomei et al. 2006).
Among the health indicators that can be used to evaluate the eects of environmental
pollution on pregnancy outcome, birth weight is one of the most useful. It marks the end
point of intrauterine growth, and low birth weight may reect fetal growth restriction,
especially if a neonate is delivered at term. It is also an indicator of infant mortality and
morbidity, and health in later life (Wells 2000).
It is well documented that birth weight of infants and the risk of low birth weight
(LBW), dened as birth weight below 2,500 g, is negatively aected by maternal exposure
to carbon monoxide (CO), sulfur dioxide (SO
), or particulate matters in the ambient air
CONTACT Anna Merklinger-Gruchala, Ph.D. Department of Pediatrics, Faculty of
Medicine, Andrzej Frycz Modrzewski Krakow University, ul. Herlinga Grudzinskiego 1, Krakow 30-705, Poland.
2017, VOL. 63, NO. 1, 7186
© 2017 Society for Biodemography and Social Biology
during pregnancy (Bobak and Leon 1999; Lin et al. 2004; Merklinger-Gruchala and
Kapiszewska 2015; Morello-Frosch et al. 2010; Stieb et al. 2012).
CO and SO
are among the major air pollutants. CO crosses the placenta rapidly,
inducing systematic oxidative stress (André et al. 2011), while SO
metabolites may act as
inhibitors of antioxidants throughout the pregnancy (Mohorovic and Micovic 2012). In
rats, such induced oxidative stress has been shown to trigger changes in vascular com-
pliance and endothelium-dependent vasoconstriction (Johnson and Johnson 2003).
Moreover, CO causes the rapid accumulation of carboxyhemoglobin and reduces the
oxygen-carrying capacity of fetal blood (Rudra et al. 2010). After CO intoxication fetal
concentrations of carboxyhemoglobin can be two-fold higher than maternal levels
(Aubard and Magne 2000). Therefore, pollution-induced placental dysfunction and
changes in the eciency of the oxygen-carrying capacity of uteroplacental blood ow
may prevent the fetus from reaching its full genetically determined growth potential.
Birth weight is also related to parity. On average, the birth weight of infants born to
primiparous women is lower than of infants delivered by multiparous women (Hinkle
et al. 2014). While the biological etiology for that nding is not clear, the reason might be
the variation in the eciency of materno-fetal exchange, which diers between primipar-
ous and multiparous women (Hafner et al. 2013). The uteroplacenta blood ow is greater
during subsequent pregnancies than it is during pregnancies involving a nulligravid uterus
(Zalud and Shaha 2008), which could result in greater observed birth weight among
infants of multiparous women.
Greater umbilical blood ow means that there is not only more ecient transport of
nutrients and oxygen to the fetus but also more ecient transport of pollutants, especially
if the maternal environment is highly polluted. This suggests that multiparous women
may be more susceptible to the eects of prenatal exposure to air pollutants than are
primiparous women. That is, greater uteroplacental blood ow in multiparous women
could actually have a harmful eect on fetal development, particularly in multiparous
women. The question thus arises whether and how parity conditions the risk of LBW
resulting from exposure to detrimental factors such as air pollution.
Our study sought to assess whether susceptibility to the eects of prenatal exposure to
air pollutants varies between multiparous and primiparous women. It did so by testing
whether multiparous women are more prone to having infants with LBW after suering
the physiological stress induced by air pollution than are primiparous women. We also
analyzed the eect of air pollutants on the odds ratio for LBW separately for each parity
group. We further tested how parity conditions the observed association between exposure
to pollution and ospringsbirth weight by adding an interaction term (air pollutant x
parity) into the full logistic regression model. Additionally, in order to verify if exposure
during early or late pregnancy is more important, we conducted trimester-specic
The study was conducted on a sample of 74,327 singleton, live, full-term infants
delivered between 1995 and 2009 by mothers whose residence at the time of infants
birth was the city of Krakow, Poland. Krakow is a densely populated metropolitan area
with unfavorable topographic locations where air pollutants are likely to accumulate.
Krakow has been among the cities most seriously threatened by air pollution not only
in Poland but also in Europe. Despite the remedial eorts that have been made, Poland is
among the European countries that contributes the most (i.e., more than 10 percent) to
the atmospheric emissions of several key pollutants: sulfur oxides, particulate matters, and
carbon monoxide, among others (European Environment Agency 2014).
Since the risk of having an infant with LBW was found to vary according to bio-
socio-economic factors such as maternal age (Reichman and Teitler 2006), parity,
marital status, education, and occupational status (Aliyu et al. 2005;Reimeetal.
2006; Shah, Zao, and Ali 2011) all of those factors were included in the analysis as
potential confounders.
The study was carried out on a sample of live, full-term infants who were delivered between
October 1, 1995 and the end of December 2009 to mothers whose residence at the time of
infants birth was the city of Krakow. Birth data were obtained from the birth registry
(Central Statistical Oce in Poland) and included: month and year of birth, birth weight (in
grams), sex of the ospring, maternal age (in years), gestational age (in weeks), parity,
maternal education (primary, lower secondary, basic vocational, upper general or specialized
secondary, and college education), maternal employment status (employed versus not
employed), and maternal marital status (married versus not married, that is single,
widow, divorced, or separated). Due to the fact that the date of birth in registration records
is restricted to month and year, the day of birth had to be assigned as 15th of a given month
for each newborn. Season of birth was dened as heating(for neonates born between
October and March) and non-heating(for those delivered between April and September).
Low birth weight (LBW) was dened as birth weight below 2,500 g, and all infants with
birth weight 2,500 g were classied as having normal birth weight (NBW).
We conducted the research on full-term live births (gestational age 3741 weeks) in order
to assess relationships in a more homogeneous sample and also to test whether ambient
pollutant levels could retard intrauterine growth. Such restriction enables us to separate eects
of retarded fetal growth from other pathophysiological causes of low birth weight that
characterize small but preterm infants (Ma and Finch 2010).
To assess exposure to ambient air pollution we used municipal ecological monitoring
data. Daily data for carbon monoxide (CO [mg/m
]) and sulfur dioxide (SO
]) from
January 1995 to December 2009 were available from the ambient air quality monitoring
network, the system maintained by the Voivodship Inspectorate for Environmental
Protection in Krakow. In 1998 its laboratory was accredited by the Polish Centre for
Accreditation for air quality monitoring testing as the rst air quality monitoring network
laboratory in Poland. The Krakow air monitoring network provides automatic continuous
measurement of air pollutants. The approximate locations of the six monitoring stations
that provided pollution data during the study period are presented in Figure 1.
We calculated the daily averages of CO and SO
on the basis of the data from the six
monitoring stations located in the city of Krakow. Among 5,479 daily averages collected
from 1 January 1995 to 31 December 2009, only 126 (2.3 percent) daily averages of CO and
160 (2.9 percent) of SO
were missing. By using recorded gestational age and date of birth,
we estimated the weekly averages of CO and SO
levels in each pregnancy. Than we
calculated the completeness of weekly averages of CO and SO
concentrations for each
pregnancy (in percentages) by dividing the number of weekly averages of each air pollutant
during a given pregnancy by the gestational age (in weeks) and multiplying by 100. The
mean levels of each pollutant during an entire pregnancy (pregnancy averages) were
calculated, but only when all weekly averages of given pollutant were available for the entire
pregnancy period (that is, when the completeness of the weekly averages of given pollutant
equalled 100 percent). All other pregnancies were removed from further analyses. Thus, the
CO-pregnancy averages and SO
-pregnancy averages were calculated for 90.9 percent and
86.1 percent of neonates respectively. Such restriction was done in order to maximize the
number of weekly averages of pollutants needed to compute the mean exposure to air
pollutants during pregnancy and thus reduce bias associated with seasonal variation.
The birth registry data included 88,476 singleton newborns, from which we
excluded stillbirths (n= 387), those with unknown gestational age (n=2),those
born below 37 or above 41 weeks of gestational age (n= 7,529), those with extremely
high or low birth weight for a given gestational age (n= 5), and those born to mothers
with unknown parity (n= 5). These exclusions left 80,548 eligible subjects. The
number of cases were further restricted to those for whom the weekly averages of
either CO or SO
was 100 percent complete, which left 74,327 subject to analyses, out
of which there were n= 15,08 (2.03 percent) neonates with LBW.
Statistical analysis
Women were divided into two categories according to their employment status:
employed and not employed. We also divided women into two categories according to
the level of education: higher education (passed at least nalhighschoolexams,which
corresponds to British A-levels, such as upper general or specialized secondary and
college education) and lower education (secondary education without nal high school
Figure 1. The approximate location of the six monitoring stations that provided air pollution data
during the study period: CENTRAL station located in the Main Square of Krakow, TRAF station situated
on a busy road, representing the trac zone, URB station, representing the northern urban background
site, IND station located in Nowa Huta eastern district, characterizing both industrial and suburban
zones, and SUB1 and SUB2 stations, representing southern urban background site.
exams, such as primary education, lower secondary, and basic vocational education).
Because maternal employment status and education were strongly associated, we calcu-
lated what we called the Emp & Edu indicator, which allowed categorizing the women
into four groups: Not EmployedLow Education(NE-LE), Not EmployedHigh
Education(NE-HE), EmployedLow Education(E-LE), and EmployedHigh
Education(E-HE), with the last one being the reference group. We also stratied
women into two categories according to the parity: primiparous, i.e., women with no
previous births (reference category) and multiparous, i.e., women with one or more
previous births.
The dierence in mean levels of air pollutants between the heating and non-heating
seasons was assessed by a ttest for dependent samples.
We examined the distribution of several known risk factors for LBW across dierent
exposure categories in order to identify potential confounders. In addition, we tested the
distribution of characteristics of singleton term births among primi- and multiparous
mothers using one-way analysis of variation (ANOVA) for continuous variable (maternal
age) and a chi-square test for categorical variables (such as sex of the ospring, marital,
employment, and educational status, Emp & Edu indicator, and season of birth).
After a descriptive analysis of the maternal-infant characteristics and their distribution
among low birth weight (LBW) and non-low birth weight (NBW) groups and among
strata of parity, we performed simple and multiple logistic regression analyses to estimate
the association of each air pollutant (CO and SO
) separately as a continuous variable with
the odds ratio (OR) for LBW.
First, only the air pollutant (CO or SO
) was entered as a predictor of LBW (crude eect).
In the second stage, we entered season of birth and maternal bio-socio-economic factors such
as maternal age (continuous), sex of the infant, parity (dichotomous), marital status (dichot-
omous), and Emp & Edu groups and tested whether there was a signicant change in the log
likelihood of delivering an infant with LBW after adding these factors to the simple model.
Because the main research question of our study was to assess if multiparous women
are more susceptible to a prenatal exposure to air pollutants than primiparous women, we
conducted the same procedure after stratication for parity. The inuence of parity on the
observed associations, i.e., eect modication by parity, was further tested by adding a
product term (air pollutant x parity) into the full logistic regression model. The interaction
(eect modication) referred to the state when the eect of one exposure (air pollutant)
on an outcome (LBW) diers across strata of another exposure (primi- and multiparous
mothers). The interaction eect was interpreted on the multiplicative scale, and it indi-
cates to what extent the eect of each air pollutant diers between primi- and multiparous
women (Buis 2010). The stratum-specic estimates together with a statement of statistical
signicance based on an appropriate test for interaction were provided, which is the most
frequently used approach when reporting interaction in case-control and cohort studies
(Knol et al. 2009).
Additionally, in order to explore critical windows of exposure, the same analyses were
performed for the eects of average air pollution levels during the rst, second, and third
trimesters of pregnancy.
Multiple comparisons were controlled by false discovery rate (FDR), which is an
expected proportion of false positives among the tests declared signicant (false plus
true). We set the maximum acceptable FDR at the level of 0.05, and calculated the
FDR-adjusted pvalues at this level to assess whether the resulting pvalues were still
statistically signicant after multiple comparisons. In our study, when analyzing the
exposure during the entire pregnancy, the same eect of each air pollutant was tested
three times: on the entire group of mothers and in the two subsamples of parity. This
is the reason that the adjustment was performed for three comparisons among the
results of the simple logistic regression analyses (crude eects)andforfourcompar-
isons among the results of the multiple logistic regression analyses (adjusted eects),
because of one additional eect of interaction (air pollutant x parity). After conducting
the trimester-specic estimates, the same eect of each pollutant was tested nine times
in crude models (three trimesters on the entire group of mothers, three trimesters on
primiparous mothers, and three trimesters on multiparous mothers) and ten times in
the adjusted models, because of one additional eect of interaction.
The results of logistic regression analyses and the test for interaction were considered
statistically signicant when the FDR-adjusted pvalue was < 0.05. The two-stage shar-
pened method was used to calculate the FDR-adjusted pvalues (Benjamini, Krieger, and
Yekutieli 2006). We used Statistica version 12.0 for the statistical analyses.
Pollutants in Krakow
From 1 January 1995 to 31 December 2009 daily concentrations of CO and SO
from 0.2 to 8.3 mg/m
, and from 1.0 to 218.5 µg/m
, respectively, with a daily average of
1.3 mg/m
(SD = 0.80) and 20.0 µg/m
(SD = 20.38), respectively. The average levels of CO
and SO
during pregnancy were strongly correlated (Pearsons correlation coecient,
r= 0.94; p< 001). The variation in both air pollutant concentrations throughout a year
was noted as similar to that found in many previous studies. In heating season the mean
levels of CO and SO
were higher than those in non-heating months (by 0.6 mg/m
18.2 µg/m
, respectively; p< 0.001, Figure 2).
The univariate analysis revealed that the OR for LBW was signicantly associated with
parity, sex of the ospring, maternal educational and employment status, and marital status,
but was not with maternal age (Table 1). Not married, not employed mothers and those
with lower educational status had a 94 percent, 59 percent, and 106 percent (respectively)
increased OR for delivering an infant with LBW (Table 1). When analyzing the educational
and employment status together, women who simultaneously had lower education and no
employment had almost three times higher risk of delivering a child with LBW than
employed women with higher education. Mothers who had a male ospring had 38 percent
lower OR for LBW than those who gave birth to females. Multiparous women in compar-
ison to primiparous mothers had reduced odds ratio for LBW by 12 percent.
The strata of parity diered in maternal age, marital, employment and educational
status, and Emp & Edu indicator but not sex of the ospring and season of birth (Table 2).
Exposure during the entire pregnancy
Crude estimates of prenatal exposure to SO
indicated slightly increased OR for LBW
among the entire group of mothers (OR = 1.01; 95% CI 1.001.01), and also in the strata
of multiparous only (OR = 1.01; 95% CI 1.011.02; Table 3). After standardization to
season of birth and maternal bio-socio-economical factors only the eect of SO
the entire group of mothers (OR = 1.01; 95% CI 1.001.01) and among the strata of
multiparous mothers remained statistically signicant (OR = 1.01; 95% CI 1.001.02).
There was no association between SO
and LBW among primiparous women. A similar
pattern was seen for exposure to CO, although the association was stronger. In crude
analysis the increased OR were seen among the entire group of mothers and multiparous
mothers alone (OR = 1.20; 95% CI 1.061.35; OR = 1.41; 95% CI 1.181.67, respectively).
Also, adjusted estimates revealed that only the eect of CO among the group of all
mothers (OR = 1.16; 95% CI 1.021.31) and among the strata of multiparous mothers
remained statistically signicant (OR = 1.28; 95% CI 1.061.54). Among primiparous
mothers the associations between CO and LBW were not statistically signicant both
before and after standardization (Table 3).
The test for interaction between exposure to CO and parity on the odds ratio for LBW
was statistically signicant (FDR-adjusted p= 0.03). The eect of one unit increase in CO
was almost 30 percent higher in multiparous than in primiparous women (OR for
interaction = 1.28; 95% CI 1.011.63). The log odds for LBW among multiparous mothers
constantly rose along with increasing CO concentrations, however only after the levels of
CO exceeded 2.4 mg/m
did the log odds became higher for multiparous than for
primiparous mothers (Figure 3). In contrast, the interaction between parity and SO
was statistically nonsignicant (FDR-adjusted p= 0.08).
Exposure in trimesters
The results of multiple logistic regressions used to assess the relationship between air
pollutant exposure in trimesters and odds ratio for LBW are presented in Table 4. Crude
estimates of prenatal exposure to SO
during the rst trimester indicated statistically
signicant but weakly increased OR for LBW among the entire group of mothers and
CO [mg/m3]
SO2 [
/m3]CO [m
Figure 2. Mean monthly sulfur dioxide (SO
) and carbon monoxide (CO) levels in Krakow city across the
study period (19952009). Winter levels are elevated in comparison with summer levels due to the
heating season (p< 0.001).
also in the strata of multiparous only mothers. After standardization, the pattern of
observed associations remained the same, that is, among all mothers (OR = 1.01; 95%
CI 1.001.01) and among multiparous mothers (OR = 1.01; 95% CI 1.001.01) we found
weakly elevated odds ratio for LBW. Exposure to SO
during the second and third
trimesters was not associated with LBW either in the group of all mothers or in either
strata of parity equally before and after standardization.
Likewise, exposure to CO during the rst trimester both before and after adjustment
was associated with OR for LBW, and the relationships were stronger than for SO
Adjusted estimates for CO exposure during this trimester were associated with 16%
increased OR for LBW among the group of all mothers (95% CI 1.031.30) and with
Table 1. Distribution of characteristics of singleton, full-term births by low birth weight status.
Characteristic Level NBW LBW OR (95% CI) pvalue
Sex of the ospring Girl n35,331 908 1.00 [reference]
% 48.5 60.2
Boy n37,488 600 0.62 (0.560.69) < 0.001
% 51.5 39.8
Parity Primiparous n39,355 864 1.00 [reference]
% 54.0 57.3
Multiparous n33,464 644 0.88 (0.790.97) < 0.001
% 46.0 42.7
Marital status Married n62,854 1153 1.00 [reference]
% 86.3 76.5
Not married n9,965 355 1.94 (1.722.19) < 0.001
% 13.7 23.5
Employment status Employed n 54,321 974 1.00 [reference]
% 74.8 65.2
Not employed n18274 520 1.59 (1.431.77) < 0.001
% 25.2 34.8
Educational status Higher n56,759 947 1.00 [reference]
% 78.2 63.5
Lower n15,830 545 2.06 (1.852.30) < 0.001
% 21.8 36.5
Emp & Edu* E-HE n45,836 753 1.00 [reference]
% 63.2 50.5
NE-HE n10,895 194 1.09 (0.921.27) 0.321
% 15.0 13.0
E-LE n8,451 219 1.57 (1.351.84) < 0.001
% 11.6 14.7
NE-LE n7,364 325 2.69 (2.353.07) < 0.001
% 10.2 21.8
Maternal age (year) n72,819 1508 1.00 (0.991.01) 0.968
Mean 28.1 28.1
SD 5.2 5.9
Season of birth Non-heating n37,018 729 1.00 [reference]
% 50.8 48.3
Heating n35,801 779 1.10 (1.001.22) 0.055
% 49.2 51.7
CO (mg/m
)n71,750 1,480 1.20 (1.061.35) 0.003
Mean 1.3 1.4
SD 0.4 0.4
)n67,942 1,410 1.01 (1.001.01) 0.009
Mean 20.4 21.1
SD 10 10
Note. *Emp & Edu indicator: NE-LE = Not EmployedLow Education, NE-HE = Not EmployedHigh Education, E-LE =
EmployedLow Education, E-HE = EmployedHigh Education.
25% increased OR for LBW among multiparous only mothers (95% CI 1.051.49),
however these results were of only borderline signicance (Table 4).
A statistically signicant relationship between exposure to CO during the third trime-
ster of pregnancy and increased OR for LBW among the group of all mothers and among
the strata of multiparous mothers observed before adjustment did not reach statistical
signicance after standardization.
Because adjusted models of analyses in trimesters revealed that both pollutants increased
OR for LBW among the entire group of mothers and among the strata of multiparous
mothers but only when exposure occurs during the rst trimester of pregnancy, we further
tested this subgroup eects by introducing the interaction term (air pollutant in rst
trimester x parity) into the full models. Although increased exposure to SO
during the
rst trimester was associated (after standardization) with LBW among multiparous mothers
and not in primiparous mothers, the test for interaction revealed that these subgroup
dierences referring to this particular time of pregnancy are not statistically signicant
(FDR-adjusted pfor interaction = 0.15). Similarly, the interaction between exposure to CO
in the rst trimester and parity was nonsignicant (FDR-adjusted pfor interaction = 0.57).
Table 2. Distribution of characteristics of singleton, full-term births stratied for parity.
Characteristic Level Multiparous Primiparous pvalue*
Sex of the ospring (n, %) Girl 16,752 49.1% 19,487 48.5% 0.072
Boy 17,356 50.9% 20,732 51.5%
Maternal age (mean, SD) 30.5 4.8 26.1 4.6 < 0.001
Marital status (n, %) Married 30,715 90.1% 33,292 82.8% < 0.001
Not married 3,393 9.9% 6,927 17.2%
Employment status (n, %) Employed 25,088 73.9% 30,207 75.3% < 0.001
Not employed 8,865 26.1% 9,929 24.7%
Educational status (n, %) Higher 25,201 74.2% 32,505 81.0% < 0.001
Lower 8,758 25.8% 7,617 19.0%
Emp & Edu** (n, %) E-HE 20,363 60.0% 26,226 65.4% < 0.001
NE-HE 4,826 14.2% 6,263 15.6%
E-LE 4,713 13.9% 3,957 9.9%
NE-LE 4,034 11.9% 3,655 9.1%
Season of birth (n, %) Heating 16,685 48.9% 19,895 49.5% 0.136
Non-heating 17,423 51.1% 20,324 50.5%
Note. *One-way ANOVA was used for continuous and chi-square test for categorical variables.
**Emp & Edu indicator: NE-LE = Not EmployedLow Education, NE-HE = Not EmployedHigh Education,
E-LE = EmployedLow Education, E-HE = EmployedHigh Education.
Table 3. Crude and adjusted odds ratios (OR) with 95% condence intervals (CI) for low birth weight
(LBW) by pollution exposure and parity.
Adjusted to bio-socio-economical factors and season of
OR FDR-adjusted pvalue OR FDR-adjusted pvalue
All 1.20 (1.061.35) < 0.01 1.16 (1.021.31) 0.02
Primiparous 1.06 (0.901.24) 0.18 1.02 (0.861.21) 0.41
Multiparous 1.41 (1.181.67) < 0.01 1.28 (1.061.54) < 0.01
All 1.01 (1.001.01) 0.01 1.01 (1.001.01) 0.02
Primiparous 1.00 (1.001.01) 0.18 1.00 (0.991.01) 0.38
Multiparous 1.01 (1.011.02) < 0.01 1.01 (1.001.02) < 0.01
0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2 2,4 2,6 2,8
CO [mg/m
Log odds for LBW
Figure 3. Log odds for LBW, as a function of exposure to CO according to parity, after controlling for
potential confounding factors (i.e., season of birth, sex of the ospring, marital status, employment
status, education, and maternal age), with assumption that all predictors are unchanged, that is, set at
the reference level (categorical variables), while maternal age (continuous) is held xed at 30 years.
Table 4. Crude and adjusted odds ratios (OR) with 95% condence intervals (CI) for low birth weight
(LBW) by pollution exposure, parity, and trimester.
Adjusted to bio-socio-economical factors and
season of birth
OR FDR-adjusted pvalue OR FDR-adjusted pvalue
CO All
Trimester 1 1.14 (1.041.25) 0.01 1.16 (1.031.30) 0.05
Trimester 2 1.06 (0.971.17) 0.17 0.99 (0.831.18) 0.93
Trimester 3 1.14 (1.041.25) 0.01 1.03 (0.871.21) 0.93
Trimester 1 1.07 (0.951.22) 0.21 1.09 (0.931.27) 0.57
Trimester 2 1.00 (0.881.14) 0.55 1.02 (0.801.29) 0.93
Trimester 3 1.01 (0.891.15) 0.55 0.93 (0.741.17) 0.91
Trimester 1 1.23 (1.071.41) 0.01 1.25 (1.051.49) 0.05
Trimester 2 1.15 (1.001.32) 0.05 0.95 (0.731.24) 0.93
Trimester 3 1.31 (1.151.50) < 0.01 1.16 (0.901.48) 0.57
Trimester 1 1.00 (1.001.01) 0.03 1.01 (1.001.01) 0.01
Trimester 2 1.00 (1.001.00) 0.69 1.00 (0.991.00) 0.45
Trimester 3 1.00 (1.001.01) 0.06 1.00 (1.001.01) 0.15
Trimester 1 1.00 (1.001.01) 0.60 1.00 (1.001.01) 0.45
Trimester 2 1.00 (0.991.00) 0.71 1.00 (0.991.00) 0.45
Trimester 3 1.00 (1.001.01) 0.56 1.00 (1.001.01) 0.45
Trimester 1 1.01 (1.001.01) < 0.01 1.01 (1.001.02) < 0.01
Trimester 2 1.00 (1.001.01) 0.58 1.00 (0.991.01) 0.61
Trimester 3 1.01 (1.001.01) 0.06 1.01 (1.001.01) 0.15
We have found that 1 mg/m
increase in carbon monoxide exposure during the entire
pregnancy was associated with a 16 percent higher odds ratio for low birth weight after
standardization to season of birth and maternal bio-socio-economic factors. Similarly, the
adjusted odds ratio for low birth weight was 1 percent higher after increasing exposure to
sulfur dioxide by 1 µg/m
during the entire pregnancy period.
These results are in accordance with previous ndings showing lower birth weight or
increased risk of LBW in term neonates whose mothers were exposed to elevated levels of
ambient CO (Lin et al. 2004; Morello-Frosch et al. 2010)orSO
during the entire
pregnancy (Bobak and Leon 1999; Geer, Weedon, and Bell 2012; Lin et al. 2004).
Considering specic windows of exposure, our study conrmed previous ndings of
increased risk after exposure to SO
during the rst trimester of pregnancy (Bobak
2000; Ha et al. 2001) but not those where elevated risk was linked with the last trimester
(Lin et al. 2004). Correspondingly, our results are in accordance with those studies that
showed an association between low birth weight and exposure to CO during the rst
trimester (Ha et al. 2001) but not during the last trimester of pregnancy (Ritz and Yu
1999). Furthermore, we noticed that the eect of exposure to CO during the entire
pregnancy on the birth weight of neonates is not the same in all mothers, but diers
according to their parity, which was conrmed by appropriate tests for interactions. The
harmful eect of CO was shown among the multiparous mothers: increase by 1 mg/m
CO was associated with 28 percent elevated odds ratio for LBW, while increasing exposure
to CO among primiparous mothers was not associated with higher risk. Our results
suggest that multiparous mothers may be more vulnerable to carbon monoxide than
primiparous mothers, which is reected in the higher probability of having a child with
birth weight below 2,500 g at term. Thus, we propose that parity may be a modier of the
association between CO and the risk of LBW, but further studies are warranted.
The nding that the ospring of multiparous women are more strongly aected by
ambient CO levels during pregnancy than the infants born to primiparous mothers
has been reported in only one previous study conducted in Los Angeles, California
(Ritz and Yu 1999). The eect of CO on birth weight was reported only for higher
parity mothers, that is, those giving birth to a second or higher-order child. High-
parity women in the 95th percentile of exposure to CO concentrations in compar-
isontowomeninthe50th percentile for last trimester exposure had almost two-
times higher odds ratio for LBW, whereas similar exposure among the entire group
of women was not associated with LBW.
The eect-measure of other chemicals having an impact on birth outcomes can also be
modied by parity. For example, peruorooctanesulfonate (PFOS) and peruorooctanoate
(PFOA), synthetic compounds or metabolites of other peruorinated chemicals that are
used in a variety of consumer products, such as nonstick pans, carpets, furniture, and
household cleaners, were associated with the ponderal index of neonates, but in the
opposite direction in the two strata of parity (Fei et al. 2008). Maternal exposure to
PFOS and PFOA were associated negatively with the ponderal index among multiparous
women but positively among nulliparous women.
It is biologically plausible that air pollutants and other toxins negatively aect birth
outcomes, especially among multiparous mothers. Parity may manipulate the
development of the placenta and placental eciency (Roland et al. 2012; Wilsher and
Allen 2003), which can be linked not only with nutrient but also toxin exchange. Greater
uteroplacental blood ow among multiparous than primiparous mothers (Zalud and
Shaha 2008) and better placental bed perfusion due to improvement of the placental
bed vascularization (Hafner et al. 2013) have been shown. In addition, a rst pregnancy
was found to result in pioneering structural changes of the internal elastic lamina in spiral
arteries, and these modications were not totally eliminated following parturition (Khong,
Adema, and Erwich 2003). The authors suggested that these residual arterial alterations
allow trophoblasts to remodel arteries more eectively in a subsequent pregnancy.
Moreover, total antioxidant capacity has been shown to be lower and oxidative stress
indicators higher in cord blood during second or subsequent pregnancies than in the null
gravid uterus (Mutlu et al. 2012). All of these morphological and physiological amend-
ments following a rst pregnancy may be responsible for the higher susceptibility of the
fetuses of multiparous mothers to environmental pollutants. It seems reasonable to
assume that when the level of CO is low, the more ecient placental blood circulation
in multiparous mothers protects them from having LBW ospring by assuring enough
nutrient and oxygen supply to the fetus. But during elevated pollutant concentrations
higher umbilical blood ow may be deleterious and outweighs the advantages of this
adaptive strategy seen when the pollution is low.
The relationship between high parity and placental eciency could also potentially
result indirectly from low socioeconomic status (SES) of the mother. Being multiparous
may be connected with poor SES and lower education (Roman et al. 2004), which in turn
can be linked with dietary calorie and/or protein deprivation (Bojar et al. 2007). Maternal
malnutrition inuences both the maternal and fetal somatotrophic axis, while nutritional
and endocrine signals can increase placental transport capacity (Fowden et al. 2009).
Many studies revealed that in mothers from nutritionally deprived populations, but also
in well-nourished women from developed countries, each subsequent pregnancy deterio-
rates the maternal condition, which may result in poor pregnancy outcome. This phe-
nomenon associated with high lifetime costs of reproduction is called the maternal
depletion syndrome(Dewey and Cohen 2007; King 2003; van Eijsden et al. 2008; Zhu
et al. 1999) and may have long-term health consequences for the mother, such as serious
metabolic disorders or even a reduced life span (Jasienska 2013).
Our study, just like all studies based on data registries, was not able to take into considera-
tion individual characteristics of women, such as dietary or smoking habits, that might
provide additional information important to consider when assessing relationships between
air pollution and LBW risk. Moreover, air pollution data based on community monitoring
systems do not provide information about variability among individualsexposure due to
occupational exposure or outdoor/indoor activity patterns. Moreover, because of no precise
geographical information on the residency of the women, we can look only at temporal
variation in air pollution and not take into consideration within-city variability in pollution
concentrations. But when considering spatial resolution assessment based on regulatory
monitoring network data we noted that the number of monitoring stations per land area in
Krakow is high (almost 6/300 km
) in comparison to other study locations, for example,
Californias South Coast Air Basin (0.6/300 km
) and even Vancouver (1.5/300 km
), which
was regarded to have very high monitor density by Marshall, Nethery, and Brauer (2008). The
high quality of the network of air pollution stations in Malopolska province and its
appropriate coverage of the Krakow residency area (six stations per 32685 ha in a city of
almost 760,000 inhabitants; Central Statistical Oce 2013) was also conrmed by a cohort
study conducted on pregnant women, the residents of the city of Krakow (Jedrychowski et al.
Whilesomeauthorsassignexposurelevels according to the monitoring station
closest to each mothers residence, the information about residence of the women
who participated in the study was not available to us and therefore we were not able to
apply modeling techniques (such as LUR models) that join together air pollution and
geographic information to characterize the variability in exposure. However, pregnant
womenlivinginmetropolitanlocationsare not exposed to pollutants only in their
place of residence, but also in their workplace, during their travel to work, and during
all other activities (shopping, visits to relatives and friends, recreational activities, etc.),
and thus their exposure might be better represented by the average, rather than by just
one station. This problem was also discussed by others (Gouveia, Bremner, and Novaes
2004). We are aware that assessing exposure in this way is connected with potential
error, but, especially given our large sample size, it is likely to be nondierential, i.e.,
to have the same magnitude and direction among LBW and NBW neonates. Moreover,
the most serious consequence of such an error is the attenuation of the eect estimated
(Kreienbrock 2007). Further, when considering the estimation of exposure for popula-
tions close to the nearest monitors location in epidemiological settings, a distance of
50 km is very often chosen as a reasonable distance for extrapolation of observed air
pollutant concentrations (Bravo et al. 2012;ODonnell et al. 2011; Spencer-Hwang
et al. 2011). The Krakow city area has a size of 18 km x 31 km and within this area
there are six monitoring stations, thus it seems rational to assume that the estimation
of exposure in our study population is reliable.
Another approach to assess individual exposure by asking participants to carry a
pollution-measuring device is a much better tool, however, it does not allow analyzing a
large sample of mothers and is unlikely that such a selected study group would be
representative of the entire population.
In summary, our research conducted on a very large population of infants suggests that
the odds ratio for LBW may vary with respect to parity and that multiparous mothers are
more susceptible to unfavorable prenatal conditions such as exposure to carbon mon-
oxide. These ndings provide additional evidence for the relationship between air pollu-
tion and LBW by identifying a vulnerable subgroup of mothers.
The ubiquity and persistence of air pollutants pose unique and emerging challenges in
addressing this public health issue. State and local public health professionals together
with reproductive health providers need to focus their eorts on reaching subpopulations
who are at high risk for prenatal exposure to environmental pollutants. One such
disadvantaged subgroup may be multiparous pregnant women.
Disclosure of potential conicts of interest
The authors declare that they have no conict of interest. This article does not contain any studies
with human participants performed by any of the authors.
This study was carried out within the Framework of a Project No. N N404 055 136, nanced by the
Ministry of Science and Higher Education.
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... These neurobehavioural deficits have been shown to predict subsequent infant development including psychomotor, cognitive and emotional development [4]. Low birth weight in infants of mothers who smoke indicates fetal growth restriction thought to be related to Carbon Monoxide (CO) exposure affecting the oxygen carrying capacity of the fetal blood [5]. Alternatives to cigarette smoking, such as nicotine replacement therapy (NRT) and ecigarettes are therefore considered by some to be a harm reduction method and information provided in healthcare leaflets for pregnant women state that nicotine alone is relatively harmless [6]. ...
... Given that infants prenatally exposed to e-cigarettes did not experience the same birth outcomes as cigarette exposed, but were similar to non-exposed infants, it could indicate a likely culprit for these negative outcomes is CO exposure, It is well established that CO exposure is associated with low birth weight [5,27]. This is due to CO binding to hemoglobin reducing blood flow and subsequently leading to growth restriction [10]. ...
Full-text available
Background Infant neurobehaviour provides an insight into the development of the central nervous system during infancy, with behavioural abnormalities highlighting a cause for concern. Research has demonstrated that prenatal exposure to cigarettes leads to deficits within neurobehavioural development, along with negative birth outcomes detrimental to subsequent development. With the growing use of e-cigarettes amongst pregnant women, this study explores how prenatal e-cigarette exposure compares to prenatal cigarette exposure. Methods Eighty-three infants were involved in the study, either exposed prenatally to cigarettes or e-cigarettes or not exposed to either. Differences were assessed between these three groups for birth outcomes and scores on the Neonatal Behavioural Assessment Scale (NBAS) at one month of age. Findings Both cigarette and e-cigarette exposed infants had a significantly greater number of abnormal reflexes (p = ·001; p = ·002). For both self-regulation and motor maturity, cigarette exposed infants performed significantly worse (p = ·010; p = ·002), with e-cigarette exposed infants having decreased motor maturity (p = ·036) abilities and marginally decreased for self-regulation (p = ·057). Birth outcomes, namely birthweight, gestation and head circumference, did not differ for e-cigarette exposed infants compared with infants who were not prenatally exposed to nicotine. Cigarette exposed infants had a significantly lower birthweight (p = ·021) and reduced head circumference (p = ·008) in comparison to non-exposed infants. Interpretation To our knowledge, this is the first research study assessing a neurological outcome as a result of e-cigarette exposure. Findings of this have potentially important implications for public health policies regarding the safety and use of e-cigarettes throughout pregnancy. Funding This research was funded by a doctoral training partnership scholarship via the ESRC, ES/P000762/1.
... First, due to women's nite reproductive resources, the number of future children that a woman can bear is inversely related to the number she has already borne. Second, the quality of future descendants is also in uenced by parity: high parity is associated with both lower birthweight (e.g., Kiely et al., 1986) and lower IQ (i.e., later-born children have lower IQ than rst-born children; see Rohrer et al., 2015), as well as with a reduced capacity to bu er fetal development against environmental stressors (Merklinger-Gruchala et al., 2017). ...
Attractiveness is a perception produced by psychological mechanisms in the mind of the perceiver. Understanding attractiveness therefore requires an understanding of these mechanisms. This includes the selection pressures that shaped them and their resulting information-processing architecture, including the cues they attend to and the context-dependent manner in which they respond to those cues. We review a diverse array of fitness-relevant cues along with evidence that the human mind processes these cues when making attractiveness judgments. For some of these cues, there is unequivocal evidence that the cue influences attractiveness judgments, but exactly why attractiveness-assessment mechanisms track that cue is an area of current debate. Another area of active inquiry is when these cues influence attractiveness judgments: because the fitness costs and benefits associated with these cues would have varied across contexts, selection should have shaped attractiveness-assessment mechanisms to be sensitive to contextual variables. As a consequence of this context-sensitive design, these mechanisms, despite being universal, should produce attractiveness assessments that vary systematically and predictably across contexts. We review evidence indicating that this is how human perception of attractiveness works, and highlight the need for more comprehensive and systematic investigations into contextual variation in human standards of attractiveness. We conclude by identifying limitations on existing evolutionary research on attractiveness, and provide concrete suggestions for how future work can address these issues.
... Based on publication records related to birth weight from the Web of Science database covering years 1904-2017 (Table 1), most studies reported in the literature focused on CAPs rather than non-criteria air pollutants . (Ebisu and Bell 2012;Hyder et al. 2014;Li et al. 2017) NO 2 75 (Darrow et al. 2011;Dedele et al. 2017;Estarlich et al. 2011) PM 10 66 (Balsa et al. 2016;Xu et al. 2011) SO 2 46 (Cho et al. 2013;Jacobs et al. 2017;Williams et al. 2007) CO 44 (Bell et al. 2007;Merklinger-Gruchala et al. 2017) O 3 42 (Chen et al. 2002;Díaz et al. 2016;Geer et al. 2012) PM 14 (Ha et al. 2017;Siddiqui et al. 2008) Nitrogen oxides (NO x ) a 13 (Bobak 2000;Malmqvist et al. 2017) Nitric oxide (NO) 9 (Coker et al. 2016;Ghosh et al. 2012) Total suspended particulate (TSP) 8 (Bobak 2000;Lee et al. 2002;Wang et al. 1997 (Quansah and Jaakkola 2009) a NO x is a generic term for mono-nitrogen oxides NO and NO 2 b A component of fine particulate matter ( c A historic measure of airborne particulate matter d PSI for five major pollutants (CO,O 3 , NO 2 , SO 2 , PM 10 ). PSI converts air pollution concentrations to a simple number between 0 and 500 and assigns descriptive terms such as Bgood^or Bmoderate^to that value ...
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Many studies have investigated associations between maternal residential exposures to air pollutants and low birth weight (LBW) in offspring. However, most studies focused on the criteria air pollutants (PM2.5, PM10, O3, NO2, SO2, CO, and Pb), and only a few studies examined the potential impact of other air pollutants on LBW. This study investigated associations between maternal residential exposure to industrial air emissions of 449 toxics release inventory (TRI) chemicals and LBW in offspring using a case-control study design based on a large dataset consisting of 94,106 LBW cases and 376,424 controls in Texas from 1996 to 2008. Maternal residential exposure to chemicals was estimated using a modified version of the emission-weighted proximity model (EWPM). The model takes into account reported quantities of annual air emission from industrial facilities and the distances between the locations of industrial facilities and maternal residence locations. Binary logistic regression was used to compute odds ratios measuring the association between maternal exposure to different TRI chemicals and LBW in offspring. Odds ratios were adjusted for child’s sex, birth year, gestational length, maternal age, education, race/ethnicity, and public health region of maternal residence. Among the ten chemicals selected for a complete analysis, maternal residential exposures to five TRI chemicals were positively associated with LBW in offspring. These five chemicals include acetamide (adjusted odds ratio [aOR] 2.29, 95% confidence interval [CI] 1.24, 4.20), p-phenylenediamine (aOR 1.63, 95% CI 1.18, 2.25), 2,2-dichloro-1,1,1-trifluoroethane (aOR 1.41, 95% CI 1.20, 1.66), tributyltin methacrylate (aOR 1.20, 95% CI 1.06, 1.36), and 1,1,1-trichloroethane (aOR 1.11, 95% CI 1.03, 1.20). These findings suggest that maternal residential proximity to industrial air emissions of some chemicals during pregnancy may be associated with LBW in offspring.
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Esse estudo teve como objetivo analisar os riscos do uso de cigarros eletrônicos durante a gravidez. Para isso, foi desenvolvida uma revisão integrativa da literatura, nas bases de dados PubMed, CINAHL e Scopus, bem como, no buscado AskMEDLINE, em julho de 2022, utilizando os termos “Cigarros eletrônicos”, “Vaping” e “Gestantes”, nos idiomas inglês, português e espanhol – adequando-os de acordo com cada base de dados. Foram encontrados 452 estudos, publicados entre 2017 e 2021, e destes, selecionados cinco para compor a amostra, após a aplicação dos critérios de seleção e leitura completa dos estudos. Como resultados, encontramos que o uso dos cigarros eletrônicos durante a gestação pode levar à redução da amamentação, recém-nascidos com baixo peso, perímetro cefálico inferior ao adequado, alterações neuromotoras e maiores índices de internação em unidades intensivas, além de outras complicações. Dessa forma, faz-se imperioso que o hábito de fumar esses cigarros sejam desestimulados e que novas investigações sejam conduzidas para ampliar esclarecimentos sobre o tema.
Previous studies have indicated that maternal exposure to particles with aerodynamic diameter <2.5 μm (PM2.5) is associated with adverse birth outcomes. However, the critical exposure windows remain inconsistent. A retrospective cohort study was conducted in Huai River Basin, Henan, China during 2013–2018. Daily PM2.5 concentration was collected using Chinese Air Quality Reanalysis datasets. We calculated exposures for each participant based on the residential address during pregnancy. Binary logistic regression was used to examine the trimester-specific association of PM2.5 exposure with preterm birth (PTB), low birth weight (LBW) and term LBW (tLBW), and we further estimated monthly and weekly association using distributed lag models. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for each 10 μg/m³ increase in PM2.5 exposure. Stratified analyses were performed by maternal age, infant gender, parity, and socioeconomic status (SES). In total, 196,780 eligible births were identified, including 4257 (2.2%) PTBs, 3483 (1.8%) LBWs and 1770 (0.9%) tLBWs. Maternal PM2.5 exposure during the second trimester were associated with the risk of PTB and LBW. At the monthly level, the PTB and LBW risks were associated with PM2.5 exposure mainly in the 4th -6th month. By estimating the weekly-specific association, we observed that critical exposure windows of PM2.5 exposure and PTB were in the 18th- 27th gestational weeks. Stronger associations were found in younger, multiparous mothers and those with a female baby and in low SES. In conclusion, the results indicate that maternal PM2.5 exposure during the second trimester was associated with PTB and LBW. Younger, multiparous mothers and those with female babies and in low SES were susceptible.
Previous studies have evaluated the relationship between prenatal air pollution exposure and low birth weight, but the results are inconsistent. The purpose of this meta-analysis is to quantitatively analyze the relationship between maternal air pollutant exposure and low birth weight (LBW). PubMed and Web of Science databases were searched to obtain the studies on the relationship between the prenatal exposure of air pollutants and LBW that published as of June 2020. The pooled effects of air pollutant exposure and LBW were calculated using random-effect model (for studies with significant heterogeneity) or fixed-effect model (for studies without significant heterogeneity). Totally, 54 studies were included in this meta-analysis. The pooled effect of PM2.5, PM10, NO2, CO, SO2, and O3 exposure on LBW were 1.081 (95% CI: 1.043, 1.120), 1.053 (95% CI: 1.030, 1.076), 1.030 (95% CI: 1.008, 1.053), 1.007 (95% CI: 1.001, 1.014), 1.125 (95% CI: 1.017, 1.244), and 1.045 (95% CI: 1.005, 1.086), respectively. NO2 (per 10 ppb increase) and CO (per 100 ppb increase) exposure in the first trimester were positively correlated with LBW, of which the pooled effect was 1.022 (95% CI: 1.009, 1. 035) and 1.008 (95% CI: 1.004, 1.012), respectively. PM2.5 (per 10 μg/m³ increase) exposure in the third trimester significantly affected the LBW, of which the pooled effect was 1.053 (95% CI: 1.010, 1.097). In addition, PM10 (per 10 μg/m³ increase) exposure in the second trimester also significantly affected the LBW, with the pooled effect of 1.011 (95% CI: 1.005, 1.017). Prenatal exposure of the major air pollutants during the entire pregnancy could increase the risk of LBW, while the susceptible window of the pollutants varied.
Although studies have assessed the associations between prenatal exposure with fine particulate matter (PM) with birth weight, few have investigated the effect of PM1 exposure and identified the susceptible exposure window. Additionally, a baby boom occurred after China implemented the universal two-child policy, but whether the effects of PM are modified by birth order remains unknown. The objective of this study was to estimate the effects of prenatal exposure to PM (PM2.5 and PM1) on birth weight, identify the susceptible exposure windows, and assess the modifying effect of birth order on the effects of PM exposure. All participants were selected from the Prenatal Environment and Offspring Health (PEOH) cohort conducted since 2016 in Guangzhou, China. A spatiotemporal land–use-regression (STLUR) model was used to estimate a pregnant woman's weekly PM2.5 exposure, and a generalized additive model (GAM) was used to estimate each PM1 exposure. A distributed lag non-linear model (DLNM) was applied to assess the exposure–lag-response associations between weekly PM exposure and birth weight. The sample included 4086 pregnant women. The results showed that maternal exposure to PM2.5 and PM1 during the 15th to 24th and 16th to 24th gestational weeks were associated with lower birth weight, the strongest association was observed in the 19th week, during which each 10 μg/m³ increment in PM2.5 and PM1 was associated with a 1.47 g (95% CI: 2.49 g, 0.44 g) and 1.58 g (95%CI: 2.74 g, 0.41 g) decrease in birth weight, respectively. Compared with the first-born neonates, greater effects of PM2.5 and PM1 exposure on birth weight were observed among the second-born neonates in the 15th to 21st and 15 h to 22nd gestational weeks. Further studies tracking the health of the second-born children are warranted because they may be more sensitive to environmental factors than the first-born children.
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Over the last 25 years, a large amount of research has been dedicated to identifying men's preferences for women's physical features, and the evolutionary benefits associated with such preferences. Today, this area of research generates substantial controversy and criticism. I argue that part of the crisis is due to inaccuracies in the evolutionary hypotheses used in the field. For this review, I focus on the extensive literature regarding men's adaptive preferences for women's waist-to-hip ratio (WHR), which has become a classic example of the just-so storytelling contributing to the general mistrust toward evolutionary explanations of human behavior. The issues in this literature originate in the vagueness and incompleteness of the theorizing of the evolutionary mechanisms leading to mate preferences. Authors seem to have rushed into testing and debating the effects of WHR on women's attractiveness under various conditions and using different stimuli, without first establishing (a) clear definitions of the central evolution concepts (e.g., female mate value is often reduced to an imprecise concept of “health-and-fertility”), and (b) a complete overview of the distinct evolutionary paths potentially at work (e.g., focusing on fecundability while omitting descendants' quality). Unsound theoretical foundations will lead to imprecise predictions which cannot properly be tested, thus ultimately resulting in the premature rejection of an evolutionary explanation to human mate preferences. This paper provides the first comprehensive review of the existing hypotheses on why men's preferences for a certain WHR in women might be adaptive, as well as an analysis of the theoretical credibility of these hypotheses. By dissecting the evolutionary reasoning behind each hypothesis, I show which hypotheses are plausible and which are unfit to account for men's preferences for female WHR. Moreover, the most cited hypotheses (e.g., WHR as a cue of health or fecundity) are found to not necessarily be the ones with the strongest theoretical support, and some promising hypotheses (e.g., WHR as a cue of parity or current pregnancy) have seemingly been mostly overlooked. Finally, I suggest some directions for future studies on human mate choice, to move this evolutionary psychology literature toward a stronger theoretical foundation.
Background Most previous studies examining associations between maternal exposures to air pollutants during pregnancy and low birth weight (LBW) in offspring focused on criteria air pollutants (PM2.5, PM10, O3, NO2, SO2, CO, and Pb). The relationship between non-criteria air pollutants and LBW is understudied and requires greater coverage. Objectives This study investigated associations between maternal residential exposure to industrial air pollutants during pregnancy and LBW in offspring. Methods This study used a case-control study design that included 94,106 term LBW cases and 376,424 controls. It covered 78 air pollutants common to both the Toxics Release Inventory (TRI) and ground air quality monitoring databases in Texas during 1996–2008. A modified version of the Emission Weighted Proximity Model (EWPM), calibrated with ground monitoring data, was used to estimate maternal residential exposure to industrial air pollutants during pregnancy. Binary logistic regression analyses were performed to calculate odds ratios (ORs) reflecting the associations of maternal exposure to industrial air pollutants and LBW in offspring, adjusted for child's sex, gestational weeks, maternal age, education, race/ethnicity, marital status, prenatal care, tobacco use during pregnancy, public health region of maternal residence, and year of birth. In addition, the Bonferroni correction for multiple comparisons was applied to the results of logistic regression analysis. Results Relative to the non-exposed reference group, maternal residential exposure to benzene (adjusted odds ratio (aOR) 1.06, 95% confidence interval (CI) 1.04, 1.08), benzo(g,h,i)perylene (aOR 1.04, 95% CI 1.02, 1.07), cumene (aOR 1.05, 95% CI 1.03, 1.07), cyclohexane (aOR 1.04, 95% CI 1.02, 1.07), dichloromethane (aOR 1.04, 95% CI 1.03, 1.07), ethylbenzene (aOR 1.05, 95% CI 1.03, 1.06), ethylene (aOR 1.06, 95% CI 1.03, 1.09), mercury (aOR 1.04, 95% CI 1.02, 1.07), naphthalene (aOR 1.03, 95% CI 1.01, 1.05), n-hexane (aOR 1.06, 95% CI 1.04, 1.08), propylene (aOR 1.06, 95% CI 1.03, 1.10), styrene (aOR 1.06, 95% CI 1.04, 1.08), toluene (aOR 1.05, 95% CI 1.03, 1.07), and zinc (fume or dust) (aOR 1.10, 95% CI 1.06, 1.13) was found to have significantly higher odds of LBW in offspring. When the estimated exposures were categorized into four different groups (zero, low, medium, and high) in the analysis, eleven of the fourteen air pollutants, with the exception of benzo(g,h,i)perylene, ethylene, and propylene, remained as significant risk factors. Conclusions Results indicate that maternal residential proximity to industrial facilities emitting any of the fourteen pollutants identified by this study during pregnancy may be associated with LBW in offspring. With the exception of benzene, ethylbenzene, toluene, and zinc, the rest of the fourteen air pollutants are identified as LBW risk factors for the first time by this study. Further epidemiological, biological, and toxicological studies are suggested to verify the findings from this study.
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The results of epidemiological studies indicate that the higher maternal exposure to air pollution, especially with particulate matter during pregnancy, the lower the infant's birth weight. The aim of this study was to estimate entire pregnancy and trimester-specific exposure of pregnant women in the city of Krakow, southern Poland, to fine particulate matter [≤10 µg (PM10)], and to assess its effect on the birth weight of boys and girls separately. The study group consisted of 85,000 singleton, live, full-term births in Krakow city during a 15-year period (data from the birth registry). The mean concentrations of the pollutant for each month of gestation were estimated using continuous municipal monitoring data. Multiple linear regression analyses indicated that the mean PM10 concentration during entire pregnancy was inversely associated with birth weight in girls and the group of boys and girls combined, after adjusting for maternal age, gestational age and year of birth; in boys the relationship was not statistically significant. Maternal exposure to PM10 during the first trimester was negatively associated with birth weight separately in girls and boys, and the group of boys and girls combined. However, the PM10 exposure during the second and third trimester of pregnancy was not associated with birth weight. PM10 air pollution at levels currently encountered in Krakow city adversely affect infant birth weight; however, the effect seems to be very small. The influence of particulate air pollution on foetal growth in early gestation is one of several possible explanations for the results, but further research is needed to establish possible biological mechanisms explaining the observed relationship.
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We hypothesized that among reproductive-age women consuming large quantities of tea, the production of estradiol would be suppressed. It has been shown that catechins and theaflavines, the major constituents of tea, inhibit aromatase, an enzyme which catalyses the conversion of androgens to oestrogens. Our study included Polish women living in urban (n 61) and rural (n 48) areas. Women collected daily saliva samples for one complete menstrual cycle and filled out dietary questionnaires. Saliva samples were analysed by RIA for concentration of 17β-estradiol (E2). Women with high (above the median) average daily consumption of black tea had reduced levels of salivary E2 in comparison with women who drank less black tea (below the median). This effect was observed within the whole study group, as well as separately within urban (P=0·0006) and rural (P=0·013) groups. High intake of the sum of subclasses of tea catechins and epigallocatechin gallate, assessed using the United States Department of Agriculture database (, was also associated with lower concentrations of E2 within all women (P=0·01 and P=0·0001, respectively) and within the urban group (P=0·0001 and P0·004, respectively). Similar relationships were observed between the sum of subclasses of theaflavines and thearubigines and E2 levels for the whole group (P=0·002) and for urban women (P=0·02). Women with high consumption of tea had lower levels of E2 concentration throughout the entire menstrual cycle. These results may have implications for reducing hormone-related cancer risk by a relatively easy dietary intervention.
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So many women who do everything right to stay healthy still wind up with breast cancer, heart disease, or osteoporosis. In The Fragile Wisdom, Grazyna Jasienska provides an evolutionary perspective on the puzzle of why disease prevention among women is so frustratingly difficult. Modern women, she shows, are the unlucky victims of their own bodies’ conflict of interest between reproductive fitness and life-long health. The crux of the problem is that women’s physiology has evolved to facilitate reproduction, not to reduce disease risk. Any trait—no matter how detrimental to health in the post-reproductive period—is more likely to be preserved in the next generation if it increases the chance of giving birth to offspring who will themselves survive to reproductive age. To take just one example, genes that produce high levels of estrogen are a boon to fertility, even as they raise the risk of breast cancer in mothers and their daughters. Jasienska argues that a mismatch between modern lifestyles and the Stone Age physiology that evolution has bequeathed to every woman exacerbates health problems. She looks at women’s mechanisms for coping with genetic inheritance and at the impact of environment on health. Warning against the false hope gene therapy inspires, Jasienska makes a compelling case that our only avenue to a healthy life is prevention programs informed by evolutionary understanding and custom-fitted to each woman’s developmental and reproductive history.
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The tested hypothesis points out that exposure to environmental toxic substances originating from coal or other fossil fuels burning is the most decisive for the impacts of the metabolic synergy of nitrogen oxides as oxidants that cause hemoglobin oxidation to methemoglobin, and sulphur dioxide metabolites as inhibitors of antioxidants, in the bloodstream through-out the period of pregnancy. The main difference between the present three-stage hypothesis and other hypotheses is the assertion that, in the pathogenesis of early and late complicated pregnancy, methemog-lobin takes on an important role. Methemoglobin by itself and from heme, redox-active ferric iron as a product of methemoglobin catabolism, has prooxi-dant properties and causes important structural and functional changes in the vascular endothelium, such as growth arrest, senescence, morphological altera-tions and cell apoptosis. Our own prospective study of methemoglobin in pregnancy revealed a significant rise and correlation between the ground level of SO 2 and the level of methemoglobin: >1.5 g/L (r = 0.72, p < 0.01) and sulfhemoglobin (r = 0.53, p < 0.05) in the bloodstream of pregnant women which can be ex-plained on the basis of an oxidant-antioxidant imba-lance (nitrogen and sulphur synergy effects), resulting in methemoglobinemia. Methemoglobinemia and preg-nancy complications like stillbirths recorded through-out the exposure period are significantly higher than those recorded in the control period (p = 0.0205), and the frequencies of reproductive loss were significantly lower in the control than in the exposure period (p < 0.05). We point out the importance of the "First-Blood circulation stage" as a new insight into the pathogenesis of the multisystemic oxidative stress and the link between a poorly perfused placenta and clinical manifestations of preeclampsia. The results suggest that the level of methemoglobin concentration in the bloodstream of pregnant women correlate with the inhalation of substances generated from coal com-bustion (SO 2 , NO x , NO, NO 2 and others) and that is an early biomarker of the identification of women with a pregnancy risk, and having an significant role upon adverse effects on mother and fetus health.
Many reproductive and developmental health problems are caused by exposure to chemicals that are widely dispersed in our environment. These problems include infertility, miscarriage, poor pregnancy outcomes, abnormal fetal development, early puberty, endometriosis, and diseases and cancers of reproductive organs. The compelling nature of the collective science has resulted in recognition of a new field of environmental reproductive health. Focusing on exposures to environmental contaminants, particularly during critical periods in development and their potential effects on all aspects of future reproductive life-course, this book provides the first comprehensive source of information bringing together the arguments that are spread out among various scientific disciplines in environmental health, clinical and public health fields. It provides a review of the science in key areas of the relationship between environmental contaminants and reproductive health outcomes, and recommendations on efforts toward prevention in clinical care and public policy.
Nulliparity is associated with lower birthweight, but few studies have examined how within-mother changes in risk factors impact this association. We used longitudinal electronic medical record data from a hospital-based cohort of consecutive singleton live births from 2002-2010 in Utah. To reduce bias from unobserved pregnancies, primary analyses were limited to 9484 women who entered nulliparous from 2002-2004, with 23 380 pregnancies up to parity 3. Unrestricted secondary analyses used 101 225 pregnancies from 45 212 women with pregnancies up to parity 7. We calculated gestational age and sex-specific birthweight z-scores with nulliparas as the reference. Using linear mixed models, we estimated birthweight z-score by parity adjusting for pregnancy-specific sociodemographics, smoking, alcohol, prepregnancy body mass index, gestational weight gain, and medical conditions. Compared with nulliparas', infants of primiparas were larger by 0.20 unadjusted z-score units [95% confidence interval (CI) 0.18, 0.22]; the adjusted increase was similar at 0.18 z-score units [95% CI 0.15, 0.20]. Birthweight continued to increase up to parity 3, but with a smaller difference (parity 3 vs. 0 β = 0.27 [95% CI 0.20, 0.34]). In the unrestricted secondary sample, there was significant departure in linearity from parity 1 to 7 (P < 0.001); birthweight increased only up to parity 4 (parity 4 vs. 0 β = 0.34 [95% CI 0.31, 0.37]). The association between parity and birthweight was non-linear with the greatest increase observed between first- and second-born infants of the same mother. Adjustment for changes in weight or chronic diseases did not change the relationship between parity and birthweight.
To evaluate the performance of placental bed vascularization in a low-risk population to predict severe pregnancy risks. Vascularization was measured in the first trimester, using 3D power-Doppler vascularization index. All women who registered during a period of 3 years for delivery in our hospital were prospectively screened in the first trimester. Power Doppler vascularization index of the placental bed (PBVI) was measured in 4325 women and correlated to 7 outcome groups: 1) normal, 2) IUGR ≤ 3rd centile, 3) delivery ≤ 34 weeks, 4) pregnancy induced hypertension (PIH), 5) all pre-eclampsia (PE), 6) severe PE, 7) severe pregnancy problems (SPP i.e. PIH or PE plus IUGR ≤ 3rd centile and/or delivery ≤ 34 weeks). In addition, measurements of mean uterine artery Doppler at 12 and 22 weeks, placental volume and PAPP-A were also performed on all women and their predictive strength for pregnancy risks was compared with the PBVI. Severe PE and SPP occurred in 0.6 vs. 1.5% of all pregnancies. First trimester PBVI below the 10th centile detected 60% of severe PE and 66.2% of SPP, the odds ratio being 4.48 (95th CI 1.98-11.82) for severe PE and 9.92 (95th CI 5.55-17.71) for SPP. Second trimester uterine artery Doppler detected 72% of PE and 50.8% of SPP, the odds ratio being 14.58 (95th CI 5.78-36.79) and 5.46 (95th CI 3.18-9.36) respectively. All other measured parameters performed much worse compared to PBVI and 22 weeks uterine artery Doppler. Placental bed vascularization index could be used for a quick and reliable first trimester assessment of severe pregnancy risks.