Effects of exposure to high levels of particulate air pollution during the follicular phase of the conception cycle on pregnancy outcome in couples undergoing in vitro fertilization and embryo transfer.

Abstract

The objective of this retrospective cohort study was to assess the potential effects of preconceptional short-term exposure to particulate air pollution in a real-world situation on pregnancy outcome in infertile women evaluating the possible role of IVF/embryo transfer treatment on this outcome using women who had conceived naturally for the first time during the same time frame as a matched control group. The study provides evidence for an association between brief exposure to high levels of ambient particulate matter (aerodynamic diameter <or=10 microm) during the preconceptional period and early pregnancy loss, regardless of the method of conception, and showed a 2.6-fold increase in risk of miscarriage, suggesting a threshold instead of a monotonic effect of this exposure on reproductive outcome.

Full text

Page 1

Effects of exposure to high levels of particulate air
pollution during the follicular phase of the conception
cycle on pregnancy outcome in couples undergoing in
vitro fertilization and embryo transfer
The objective of this retrospective cohort study was to assess the potential effects of preconceptional short-term
exposure to particulate air pollution in a real-world situation on pregnancy outcome in infertile women evaluating
the possible role of IVF/embryo transfer treatment on this outcome using women who had conceived naturally for
the first time during the same time frame as a matched control group. The study provides evidence for an associ-
ation between brief exposure to high levels of ambient particulate matter (aerodynamic diameter %10 mm) during
thepreconceptionalperiodandearlypregnancyloss,regardlessofthemethodofconception,andshoweda2.6-fold
increase in risk of miscarriage, suggesting a threshold instead of a monotonic effect of this exposure on reproduc-
tive outcome. (Fertil Steril?2010;93:301–3. ?2010 by American Society for Reproductive Medicine.)
The preimplantation period of development represents a critical
time during which the embryo is highly susceptible to exogenous
insults that can affect future growth and developmental potential,
either prenatally or postnatally (1, 2). Previous experimental
studies conducted in our laboratory have provided evidence
that both short-term and long-term exposure to particulate air
pollution has a significant impact on female reproductive func-
tion, affecting embryonic development before and after implanta-
tion. Preconception acute exposure to diesel exhaust particles
(DEP) and chronic exposure to fine particulate matter (PM; diam-
eter %2.5 mm, PM2.5) present in ambient air were implicated in
the disruption of the segregation pattern of the inner cell mass
(ICM) and trophectoderm cell lineages at the blastocyst stage,
an important marker of embryo viability and developmental
potential (3, 4). Defective embryonic development after implan-
tation resulted in an increased number of implantation failures,
decreased number of viable fetuses, and higher rates of
miscarriage (5, 6).
Despite the ubiquitous and unavoidable nature of traffic-related
particulate air pollution exposure in metropolitan areas and the pos-
sibility of women trying to conceive, naturally or otherwise, being
exposed to high concentrations of environmental toxins during this
period, at present no studies focused on the effects of this exposure
on early embryo development. Therefore, the current study was de-
signed to assess the potential effects of short-term exposure to
particulateairpollutionduringthefollicularphaseoftheconception
cycle on pregnancy outcome in infertile women evaluating the pos-
sible role of IVF/embryo transfer treatment on this outcome using
women who had conceived naturally for the first time during the
same time frame as a matched control group.
The outcome of clinical pregnancies achieved after IVF treat-
ment of infertile patients (study group; n ¼ 177) or spontaneous
conception (control group; n ¼ 354) between January 1, 1997
and December 31, 2006 was compared. The retrospectivematched
(1:2) study was approved by our institutional review board (IRB)
and written informed consent was provided by all participants.
The median age of the women showed no difference between
groups. Pregnancies in the control group were selected from our
obstetric database if they met the following criteria: [1] first preg-
nancy; [2] similar last menstrual period (LMP; LMP ? 2 days) for
everypatientinthecontrolgroupwithregardtothestudygroup;[3]
regular menstrual cycle (28 ? 2 days) before pregnancy; and [4]
same ethnicorigin (white) and socioeconomic stratum as the study
group.AllpatientslivedintheS~ aoPaulometropolitanareaandhad
noprevioushistoryofsmoking,chronicdiseases,medications,and
abuseof alcoholor drugs. Pregnancy outcome measurements were
the first trimester loss (fetal loss before 12 weeks) or term preg-
nancy (delivery R37 weeks of gestation). No second trimester
pregnancy losses were observed in this study.
Daily records of PM10concentrations during the study period
were taken from 14 monitoring stations covering nearly all areas
of the city and the arithmetic average of PM10across all monitor-
ing stations was considered representative of the citywide
Paulo Marcelo Perin, M.D., Ph.D.a,c
Mariangela Maluf, M.D., Ph.D.a,c
Carlos Eduardo Czeresnia, M.D.c,d
Daniela Aparecida Nicolosi Foltran Janu? ario, B.Sc.b,c
Paulo Hil? ario Nascimento Saldiva, M.D., Ph.D.a
aDepartment of Pathology, University of S~ ao Paulo School of
Medicine
bDepartment of Experimental Physiopathology, University of
S~ ao Paulo School of Medicine
cDivision of Reproductive Medicine, CEERH—Specialized
Center for Human Reproduction
dDivision of Reproductive Medicine, C? elula Mater, S~ ao Paulo,
Brazil
Received February 17, 2009; revised and accepted June 16, 2009;
published online July 23, 2009.
P.M.P. has nothing to disclose. M.M.has nothing to disclose. C.E.C. has
nothing to disclose. D.A.N.F.J. has nothing to disclose. P.H.N.S. has
nothing to disclose.
Reprint requests: Paulo Marcelo Perin, M.D., Division of Reproductive
Medicine, CEERH—Specialized Center for Human Reproduction,
R. Mato Grosso, n. 306, 19th floor, S~ ao Paulo 01243-0020, Brazil
(FAX: 55-11-3258-0008; E-mail: paulo@ceerh.com.br).
0015-0282/10/$36.00
doi:10.1016/j.fertnstert.2009.06.031
Fertility and Sterility?Vol. 93, No. 1, January 2010
301
Copyright ª2010 American Society for Reproductive Medicine, Published by Elsevier Inc.

Page 2

exposure status. The short-term PM10average concentration for
the 14 days postdating each patient’s LMP was determined as
the average follicular phase exposure for both the study and con-
trolgroupstorepresenttheexposureofinterest.ThePM10wascat-
egorized into quartiles (Q1: %30.48 mg/m3, Q2: 30.49–42.00 mg/
m3, Q3: 42.01–56.72 mg/m3, and Q4: >56.72 mg/m3) and exposure
risk was divided into two periods according to the months of the
year in which average concentrations and confidence intervals
(CI) for PM10were in the upper quartile (Q4period) or not (Q1–
Q3period) and exceeded health-based national air quality standard
of 50 mg/m3annual mean (7). The Q4period coincided with the
winter months (June through August) in Brazil.
Multivariate logistic regression was used to evaluate the effect of
follicular phase PM10exposure period and age on pregnancy out-
come. Theriskof early pregnancy lossinthe study and controlpop-
ulations was compared using the Mantel-Haenszel method. The
effect of follicular phase PM10exposure either as a continuous or
a categorical variable was expressed as an odds ratio (OR) with
95% CI and associated P values. The data were analyzed using
the Statistics Package for Social Sciences version 13.0 (SPSS Inc.,
Chicago, IL).
Nosignificant modificationinthe riskofearly pregnancy lossac-
cording to baseline exposure (first PM10quartile) was seen for each
interquartile range increase up to the third quartile. However, follic-
ularphaseexposuretoPM10averagelevelobservedinthelastquar-
tile significantly increased the OR (Wald Z-value ¼ 5.53; P¼.019;
OR: 2.90) for early pregnancy loss in the expectant population. For
the logistic regression model, the risk of early pregnancy loss in-
creased 3% per unit increase in follicular phase PM10(Wald Z-
value ¼ 17.97; P¼.000; OR: 1.03). Based on this observation
and the a priori assumption that early pregnancy loss risk could
be increased during thewinter months, the Q1–Q3periods werecol-
lapsedintoa singlegroup(Q1–Q3period). Theearly pregnancy loss
and live birth rates for both study and control patients are shown in
Table 1. The OR obtained was 2.58 (95% CI: 1.63–4.07; c2¼
16.75; P¼.000), showing that for women exposed to the Q4period
during the follicular phase of their conception cycle, the risk of
early pregnancy loss was increased 2.6-fold, regardless of the
method of conception. Odds ratios were 2.72 (95% CI:
1.51–4.89) and 2.32 (95% CI: 1.00–5.43) for control and study
patients, respectively, and no heterogeneity was observed across
groups.
In the current study we found that early pregnancy loss rates
among patients that conceived either spontaneously or after IVF/
embryotransfertreatmentandwereexposedtoQ1–Q3periodsdur-
ing the follicular phase of their conception cycle were similar
(13.7% and 14.5%, respectively) and in accordance with the rates
of reported miscarriage (12%–15%) that occur in the general pop-
ulation (8). Conversely, the risk of early pregnancy loss in women
exposedtohighlevelsofambientPM10(Q4period)during thepre-
conceptionalperiodwas2.6-foldhigherthanexpectedinthegroup
of women exposed to lower levels of ambient PM10(Q1–Q3pe-
riods) independently of the mode of conception (by IVF/embryo
transfer, 2.32; by spontaneous conception, 2.72). In the group of
patientsexposedtohighlevelsofambientPM10(Q4period)during
the preconceptional period, similar rates of spontaneous miscar-
riage observed in patients who achieved pregnancy spontaneously
or through IVF/embryo transfer (30.2% and 28.3%, respectively)
led us to conclude that infertile women were not more susceptible
than fertilewomen totheeffects ofthe exposure onpregnancyout-
come. The results of this study bring into the clinical arena what
previousexperimentalobservationsinvolvingmiceshowed—asig-
nificant decrease in the number of viable mouse fetuses and an in-
crease in the number of implantation failures in animals
chronically exposed to air pollution (5). The observation of
athresholdinsteadofamonotoniceffectofambientPM10exposure
on reproductive outcome may suggest that female gametes, due to
a functional compartmentalization, are more protected and less
susceptible to direct effects of PM10than the cardiorespiratory
system.
Thedisruptionofthenormalsegregationpattern ofthe firsttwo-
celllineagesattheblastocyststage,aswellasthelossofICMmor-
phological integrity, have been documented in an experimental
model used by our group for the evaluation of the effects of
short-term exposure to DEP on fertilization and embryo develop-
ment invitro (4). The size of first two-cell lineages, as well as their
ratio, influence future growth, viability, and implantation potential
of the blastocyst (1, 9, 10). Based on our experimental data and on
these findings we hypothesize that the lineage specification defect
and the loss of ICM integrity may suggest one of the possible
TABLE 1
Pregnancy outcome by particulate matter (PM10) exposure during the follicular phase after natural or IVF conception.
Conception Pregnancy outcome
Exposure
Q1–3periodQ4period
No.%No.%
Natural
First trimester loss
Term pregnancy
34
214
13.7
86.3
32
74
30.2
69.8
IVF
First trimester loss
Term pregnancy
18
106
14.5
85.5
15
38
28.3
71.7
c2¼ 16.75; P ¼ .000; odds ratio ¼ 2.582.
Perin. Correspondence. Fertil Steril 2010.
302
Perin et al.
Correspondence
Vol. 93, No. 1, January 2010

Page 3

pathways through which increased risk of early pregnancy loss is
triggered in women exposed to high levels of ambient PM10.
The current study benefited from the methodological and statis-
tical approaches through which we controlled specific characteris-
tics of study and control populations that could bias the observed
effects by associations of exposure and outcome to confounding
variables. The selection of pregnant patients in the control group
with a regular menstrual cycle interval (? 28-day cycle) and
known LMP (confirmed by ultrasound), who were exposed to
ambient PM10during the same time-frame as case patients (with
follicular phase duration precisely known), significantly reduced
the exposure to misclassification despite the retrospective nature
of the analysis. To properly analyze the complex and interrelated
nature of the IVF/embryo transfer treatment dependent variables,
multiple logistic regression was selected as the statistical method
to assess the effects of different ovarian response patterns to
gonadotrophins, exposure, patient’s age, and the year of IVF treat-
ment, as well as their interactions in this case-control study, elim-
inating the possibility of an observed effect being caused by
chance (type I error). However, we do recognize some limitations
toourstudy.Exposureassessmentwaslimitedbecauseweusedthe
ambientPM10levelsderivedfromanetworkaverageacrossanum-
ber of sites in the city, an approach that could introduce some bias
by not considering geographic microclimate differences in
exposure (11). The selection of a single pollutant from a complex
mixture of compounds present in air pollution to evaluate its
effects on IVF/embryo transfer pregnancy outcome may represent
another important source of bias, as the reported effect may be
attributed to other pollutants. Finally, extrapolation of the results
to the general population may be limited because our population
lived in areas of higher socioeconomic status and had the same
ethnic origin—two important covariates that may influence and
interact with environmental conditions (12).
To our knowledge, this is the first study of its kind conducted to
evaluate the possible effects of preconceptional short-term expo-
sure to ambient PM10on pregnancy outcome of infertile women
undergoing IVF/embryo transfer who live in a large metropolitan
area. The results presented here provide evidence for an associa-
tion between brief exposure to high levels of ambient PM10during
the preconceptional period and early pregnancy loss, regardless of
the method of conception and show for the first time a threshold
instead of a monotonic effect of ambient PM10exposure on repro-
ductive outcome. The 2.6-fold increase in the risk of early preg-
nancy loss during the winter time has potential public health
implications and warrants stronger environmental policies aimed
at reducing urban air pollution during this period. To avoid con-
ceiving during high pollution alerts issued by environmental
agencies would be a wise approach.
REFERENCES
1. FlemingT,KwongW,PorterR,UrsellE,FesenkoI,
WilkinsA,etal.Theembryoanditsfuture.BiolRe-
prod 2004;71:1046–54.
2. Xu G, Umezawa M, Takeda K. Early development
origins of adult disease caused by malnutrition
and environmental chemical substances. J Health
Sci 2009;55:11–9.
3. MalufM,PerinP,Janu? ario D,SaldivaP.Invitro fer-
tilization, embryo development, and cell lineage
segregation after pre- and/or postnatal exposure of
female mice to ambient fine particulate matter. Fer-
til Steril. Published online October 23, 2008 [Epub
ahead of print].
4. Perin P, Maluf M, Janu? ario D, Saldiva P. Effects
of short-term exposure of female mice to diesel
exhaust particles on in vitro fertilization and em-
bryo development. Fertil Steril 2008;90(Suppl 1):
S206.
5. Mohallem S, Lobo D, Pesquero C, Assunc x~ ao J,
Andre P, Saldiva P, et al. Decreased fertility in
mice exposed to environmental air pollution in the
city of Sao Paulo. Environ Res 2005;98:196–202.
6. Silva I, Lichtenfels A, Pereira L, Saldiva P. Effects
of ambient levels of air pollution generated by traf-
fic on birth and placental weights in mice. Fertil
Steril 2008;90:1921–4.
7. CETESB. Companhia de Tecnologia de Sanea-
mento Ambiental (S~ ao Paulo State Environmental
Protection Agency). Poluentes do ar. S~ ao Paulo:
Secretaria de Estado do Meio Ambiente do Gov-
erno do Estado de S~ ao Paulo, 2006. Available at:
http://wwwcetesbspgovbr/Ar/ar_saudeasp.
8. Zinaman M, Clegg E, Brown C, O’Connor J,
Selevan S. Estimates of human fertility and preg-
nancy loss. Fertil Steril 1996;65:503–9.
9. Kovacic B, Vlaisavljevic V, Reljic M, Sajko M. De-
velopmental capacity of different morphological
types of day 5 human morulae and blastocysts. Re-
prod Biomed Online 2004;8:687–94.
10. RichterK,HarrisD,DaneshmandS,ShapiroB.Quan-
titative grading of a human blastocyst: optimal inner
cellmasssizeandshape.FertilSteril2001;76:1157–67.
11. Ritz B, Wilhelm M. Ambient air pollution and
adverse birth outcomes: methodologic issues in an
emerging field. Basic Clin Pharmacol Toxicol
2008;102:182–90.
12. Briggs D. Environmental pollution and the global
burden of disease. Br Med Bull 2003;68:1–24.
Fertility and Sterility?
303