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Human sex ratio at amniocentesis and at birth in Taiwan

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Objectives: An increase in the proportion of male-to-female live births has raised concerns in Taiwan. Disclosure of fetal sex during prenatal screening is not allowed by the Taiwan government. Fetal sex annotation in clinical genetic reports is also prohibited. This study tested the hypothesis that the male-to-female sex ratio at amniocentesis should be lower than the sex ratio at birth, if a certain percentage of female fetuses are being selectively aborted after amniocentesis. Therefore, we examined the differences between fetal sex ratio at amniocentesis at a tertiary medical center in southern Taiwan and the nationwide sex ratio at birth in Taiwan from 1992 to 2011. Materials and methods: Data of normal male and female karyotypes during the study period were collected from the cytogenetic laboratory of the National Cheng Kung University Hospital (NCKUH) in southern Taiwan. Data of sex ratio at birth nationwide in Taiwan were obtained from the Department of Statistics, Ministry of the Interior, Taiwan. We calculated 95% binominal confidence intervals for the sex ratios and differences between fetal sex ratio at amniocentesis, and nationwide sex ratio at birth were tested by the χ(2) test and Bonferroni correction. Results: The nationwide sex ratio at birth ranged from 1.07 to 1.11 during the period from 1992 to 2011 in Taiwan, with the highest in 2004 and the lowest in 1993. The fetal sex ratio at amniocentesis at NCKUH ranged more widely (0.82-1.28), with the lowest in 1993 and the highest in 2007. After regression analysis, both trends of sex ratio at amniocentesis during midtrimester and at birth were not significantly increased by years. Furthermore, the sex distribution at amniocentesis during midtrimester did not differ significantly from the nationwide sex ratio at birth (1.113 vs. 1.092, p = 0.151). Conclusions: The results showed that sex ratio was already skewed toward male at midtrimester. Our data imply that artificial sex selection, if it were present, might have already emerged prior to the timing of amniocentesis. However, more large nationwide studies on sex ratios in Taiwan are warranted.
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Original Article
Human sex ratio at amniocentesis and at birth in Taiwan
I-Wen Lee
a,b,c,e
, Yi-Chun Lai
a
, Pao-Lin Kuo
a,c,e,
**, Chia-Ming Chang
d,e,
*
a
Department of Obstetrics and Gynecology, National Cheng Kung University Hospital, Tainan, Taiwan
b
Institute of Biotechnology, National Cheng Kung University, Tainan, Taiwan
c
Cytogenetic Laboratory, Department of Pathology, National Cheng Kung University Hospital, Tainan, Taiwan
d
Department of Internal Medicine, National Cheng Kung University Hospital, Tainan, Taiwan
e
Department of Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
Accepted 2 March 2012
Abstract
Objectives: An increase in the proportion of male-to-female live births has raised concerns in Taiwan. Disclosure of fetal sex during prenatal
screening is not allowed by the Taiwan government. Fetal sex annotation in clinical genetic reports is also prohibited. This study tested the
hypothesis that the male-to-female sex ratio at amniocentesis should be lower than the sex ratio at birth, if a certain percentage of female fetuses
are being selectively aborted after amniocentesis. Therefore, we examined the differences between fetal sex ratio at amniocentesis at a tertiary
medical center in southern Taiwan and the nationwide sex ratio at birth in Taiwan from 1992 to 2011.
Materials and Methods: Data of normal male and female karyotypes during the study period were collected from the cytogenetic laboratory of
the National Cheng Kung University Hospital (NCKUH) in southern Taiwan. Data of sex ratio at birth nationwide in Taiwan were obtained from
the Department of Statistics, Ministry of the Interior, Taiwan. We calculated 95% binominal confidence intervals for the sex ratios and
differences between fetal sex ratio at amniocentesis, and nationwide sex ratio at birth were tested by the c
2
test and Bonferroni correction.
Results: The nationwide sex ratio at birth ranged from 1.07 to 1.11 during the period from 1992 to 2011 in Taiwan, with the highest in 2004 and
the lowest in 1993. The fetal sex ratio at amniocentesis at NCKUH ranged more widely (0.82e1.28), with the lowest in 1993 and the highest in
2007. After regression analysis, both trends of sex ratio at amniocentesis during midtrimester and at birth were not significantly increased by
years. Furthermore, the sex distribution at amniocentesis during midtrimester did not differ significantly from the nationwide sex ratio at birth
(1.113 vs. 1.092, p¼0.151).
Conclusions: The results showed that sex ratio was already skewed toward male at midtrimester. Our data imply that artificial sex selection, if it
were present, might have already emerged prior to the timing of amniocentesis. However, more large nationwide studies on sex ratios in Taiwan
are warranted.
Copyright Ó2012, Taiwan Association of Obstetrics & Gynecology. Published by Elsevier Taiwan LLC. All rights reserved.
Keywords: prenatal sex determination; sex discrimination; sex ratio
Introduction
Sex ratio, defined as the ratio of males to females in
a population, is assumed to be close to 1:1. In humans, the
natural sex ratio at birth remains a controversial issue for
biologists. Considering the fact that male fetuses are more
vulnerable to life-threatening insults than females, it has
been postulated that the natural sex ratio at birth should be
slightly higher than 1. In reality, the worldwide sex ratio at
birth is approximately 105 boys per 100 girls [1e3].
However, statistics from a number of government databases
have shown that sex ratios at birth have been skewed
recently [4e7]. Human sex ratio after birth has also been
reported to be relevant to the variation of life expectancy
and mortality [8].
* Corresponding author. Department of Internal Medicine, National Cheng
Kung University Hospital, 138 Sheng-Li Road, Tainan 70403, Taiwan.
** Corresponding author. Division of Genetics, Department of Obstetrics and
Gynecology, National Cheng Kung University Hospital, 138 Sheng-Li Road,
Tainan 70403, Taiwan.
E-mail addresses: paolink@mail.ncku.edu.tw (P.-L. Kuo), cmchang@mail.
ncku.edu.tw,tw.charming@gmail.com (C.-M. Chang).
Available online at www.sciencedirect.com
Taiwanese Journal of Obstetrics & Gynecology 51 (2012) 572e575
www.tjog-online.com
1028-4559/$ - see front matter Copyright Ó2012, Taiwan Association of Obstetrics & Gynecology. Published by Elsevier Taiwan LLC. All rights reserved.
http://dx.doi.org/10.1016/j.tjog.2012.09.012
Generally, sex ratios at birth are lower than 1 in developed
countries at higher altitudes, such as the United States,
Canada, and Europe [4e7]. By contrast, sex ratios at birth are
consistently higher than 1 in developing countries with
cultural preferences that favor the birth of males over females.
In Asian countries, such as China, the predominant male-to-
female ratio at birth has been postulated as a result of selec-
tive abortion of female fetuses by prenatal sex determination
[9,10]. Skewed sex ratios have also been reported in immi-
grants from India to Norway [11]. However, the sample sizes
in that study were too small to draw definitive conclusions of
a preference for sex-selective abortion among mothers of
Indian origin [11].
Notably, in China, a country in which the birth of more than
one baby is prohibited by strict national policy, Zhu et al have
found that the ratio of boys to girls in rural areas of China was
as high as 120:100 [10]. Sex ratios in several countries have
also shown significant transitions in the past few decades [6],
and skewing of sex ratios at birth has been reported to be an
indicator of sex discrimination, which may violate basic
human rights [9].
An increase in the proportion of male-to-female live births
has raised concerns in Taiwan recently. Prenatal fetal sex
disclosure is strictly prohibited in all clinical settings by the
Taiwan government. Clinicians have been officially banned
from responding directly to parents who ask the question “Is it
a girl or a boy?” In addition, fetal sex annotation has also been
prohibited in all clinical genetic reports after August, 2011 [12].
In order to investigate the fetal sex ratio issue, the objective
of this study was to assess the difference between fetal sex
ratio at a tertiary medical center and the nationwide sex ratio
at birth in Taiwan. The null hypothesis of this study is that
fetal sex ratio at amniocentesis is not different to the sex ratio
at birth. On the contrary, the alternative hypothesis is that fetal
sex ratio at amniocentesis is different from the sex ratio at
birth, which implies a certain percentage of female fetuses are
being selectively aborted after fetal sex has been disclosed at
midtrimester.
Material and methods
Feral sex ratio at amniocentesis
All prenatal karyotyping results obtained during the period
from 1992 to 2011 at the Cytogenetic Laboratory of the
National Cheng Kung University Hospital (NCKUH),
a tertiary medical center in southern Taiwan, were retrieved
and analyzed. Fetal sex ratios at amniocentesis were calculated
by dividing the number of fetuses with a normal male
karyotype (46,XY) by the number of fetuses with a normal
female karyotype (46,XX). Fetuses with aneuploidy or trans-
locations were excluded. Maternal and fetal characteristics
that were analyzed in this study included maternal age, indi-
cations for amniocentesis, date of amniocentesis, and gesta-
tional age of the fetus at the time of amniocentesis. This study
was approved by the institutional review boards from
NCKUH.
Sex ratio at birth
The sex ratio at birth in each year of the study period was
defined as the ratio of all boys to all girls aged <1 year
registered in the Department of Statistics, Ministry of the
Interior, Administrative Yuen, Taiwan, ROC.
Statistical analysis
We calculated the 95% binominal confidence intervals
(CIs) for the sex ratios by using the 95% CI for the proportion
of male births or fetuses with normal male karyotype (pf) with
a variance of pf (1 epf). The sex ratios and 95% binominal
CIs were determined with the quadratic formula as reported by
Spiegel (1961) for binomial CIs for proportions. Differences
between fetal sex ratio at amniocentesis and sex ratio at birth
were tested by the c
2
test and Bonferroni corrections [13].
Differences were considered statistically significant with a p
value <0.05.
Results
As illustrated in Fig. 1, the trends in sex ratio in Taiwan
during the period from 1992 to 2011 were examined by
regression analysis. First, the nationwide sex ratio at birth was
not increased or decreased for 20 years (y ¼0.0002x þ0.6253;
R
2
¼0.0334, NS). Second, the sex ratio at amniocentesis at
NCKUH during the 20 years was not significantly increased
(y ¼0.091x e17.108; R
2
¼0.2394, NS). Although the fetal sex
Fig. 1. Trends of sex ratio at amniocentesis and at birth. -The national sex
ratio at birth was defined as the ratio of all boys to all girls aged <1 year
registered in the Department of Statistics, Ministry of the Interior. Data were
retrieved from Statistical Year Book of Interior, published by Department of
Statistics, Ministry of the Interior, Executive Yuan, Taiwan, R.O.C., at http://
sowf.moi.gov.tw/stat/year/elist.htm, accessed on January 15, 2012. AFetal
sex ratios at amniocentesis were calculated by dividing the number of fetuses
with a normal male karyotype (46, XY) by the number of fetuses with
a normal female karyotype (46, XX). All prenatal karyotyping results were
obtained during the period 1990 to 2010 at the cytogenetic laboratory of the
National Cheng Kung University Hospital but fetuses with aneuploidy or
translocations were excluded. NS ¼not significant.
573I-W. Lee et al. / Taiwanese Journal of Obstetrics & Gynecology 51 (2012) 572e575
ratio at amniocentesis seemed to increase more than the human
sex ratio at birth nationwide during the study period of two
decades, the difference in both trends was not statistically
significant.
As shown in Table 1, the nationwide sex ratio at birth in
Taiwan remained constant at 1.08 during the period from 1992
to 2011, with the highest at 1.1057 in 2004 and the lowest at
1.0759 in 1993. Overall, there was no significant difference in
sex distribution between the NCKUH data and the nationwide
data (1.113 vs. 1.092, p¼0.110). Although the fetal sex ratios
at amniocentesis were significantly different to the nationwide
sex ratio at birth in 1994, 1997, and 2002, as tested by the c
2
test using the threshold of p0.05, all were nonsignificant
after Bonferroni correction using the corrected threshold of
p0.001.
In addition, the average maternal age at amniocentesis
ranged from 32.4 years to 35.33 years at NCKUH from 1992
to 2011, while the average maternal age ranged from 26.4
years in 1998 to 29.8 years in 2008. Of interest, the maternal
age at amniocentesis at NCKUH was higher than that
nationwide at birth because more than half the mothers
received amniocentesis due to advanced maternal age.
Discussion
The trends in sex ratio at birth in Taiwan during the period
from 1992 to 2011 remained constant at 1.08. Our result shows
that the fetal male-to-female sex ratio at amniocentesis
increased no more than the sex ratio of newborn babies in
Taiwan. In addition, the mothers who underwent prenatal
diagnosis were older. Our findings imply that the so-called
selective abortion of female fetuses after amniocentesis is
not true; at least at a tertiary medical center in southern
Taiwan, where people are considered to be more traditional
and conservative than northern Taiwan.
Changes in sex ratio at birth have been attributed to many
different factors, including maternal age at menarche, parental
ages, birth order, race, and preference of boys or girls
[3,5,7,14e16]. By contrast, data from most countries in
Europe and North America show that the male-to-female ratio
of second-order births is lower than that of first-order births
[4,6]. Globally, the differences in human natal sex ratio are
positively correlated with life expectancy, indicating that the
natal sex ratio is influenced by existing environmental condi-
tions and perceived future survival [8,17]. Advocates and
governments seeking to reverse this imbalance have prohibited
sex detection tests and/or sex-selective abortion [9] in the hope
that these measures would reverse the trend. Such policies
have been difficult to enforce, however, and have met with
only limited success [18,19].
Taiwan is located off the coast of southeastern China and
shares a Han Chinese heritage. One of the most distinguishing
culture features of the Han Chinese, both in China and in
Taiwan, is the existence of a patrilineal society in which
married daughters belong to the husband’s family, and fami-
lies tend to prefer boys to girls. In some instances, in China as
well as in countries with low fertility rates, data on sex ratio at
birth are affected by generalized and systematic under-
Table 1
Comparison of sex ratio at amniocentesis and at birth.
Year Maternal age at
amniocentesis
(y; mean SD)
Numbers of karyotype reports of fetus Boys/girls <1 y old in national population in Taiwan
a
46,XY 46,XX Sex ratio at amniocentesis
(95% CI
c
)
Boys born Girls born Sex ratio at birth
(95% CI)
b
pvalue
1992 34.45 4.25 47 50 0.94 (0.63e1.40) 160,372 147,360 1.09 (1.08e1.10) 0.471
1993 33.65 4.80 71 87 0.82 (0.60e1.12) 159,265 148,027 1.08 (1.07e1.08) 0.083
1994 32.46 6.48 117 137 0.85 (0.67e1.09) 153,609 140,085 1.10 (1.09e1.11) 0.047
c
1995 32.50 4.94 150 155 0.97 (0.77e1.21) 157,466 145,612 1.08 (1.07e1.09) 0.332
1996 32.40 4.93 312 273 1.14 (0.97e1.34) 158,284 145,553 1.09 (1.08e1.10) 0.549
1997 32.65 5.01 455 357 1.28 (1.11e1.46) 160,299 147,107 1.09 (1.08e1.10) 0.027
c
1998 32.40 5.15 568 520 1.09 (0.97e1.23) 132,759 122,017 1.09 (1.08e1.10) 0.949
1999 32.87 4.87 848 784 1.08 (0.98e1.19) 141,105 129,112 1.09 (1.09e1.10) 0.835
2000 33.12 4.88 983 918 1.07 (0.98e1.17) 153,054 139,670 1.10 (1.09e1.10) 0.616
2001 32.40 5.13 1019 905 1.13 (1.03e1.23) 128,338 118,043 1.09 (1.08e1.10) 0.445
2002 32.43 5.11 1024 849 1.21 (1.10e1.32) 123,895 112,792 1.10 (1.09e1.11) 0.045
c
2003 32.62 5.10 904 799 1.13 (1.03e1.24) 114,018 103,438 1.10 (1.09e1.11) 0.593
2004 32.61 5.03 989 888 1.11 (1.02e1.22) 108,663 98,273 1.11 (1.10e1.12) 0.876
2005 32.74 5.52 936 870 1.08 (0.98e1.18) 101,864 93,467 1.09 (1.08e1.10) 0.785
2006 33.28 5.11 1025 932 1.10 (1.01e1.20) 100,859 92,028 1.10 (1.09e1.11) 0.939
2007 35.33 1.15 1278 1,109 1.15 (1.06e1.25) 100,434 91,587 1.10 (1.09e1.11) 0.229
2008 NA 1268 1,164 1.09 (1.01e1.18) 98,038 89,530 1.10 (1.09e1.11) 0.899
2009 33.54 4.33 1318 1,136 1.16 (1.07e1.26) 94,987 87,612 1.08 (1.07e1.09) 0.096
2010 33.49 4.61 1301 1,189 1.09 (1.01e1.18) 82,126 75,156 1.09 (1.08e1.10) 0.974
2011 33.68 4.13 1310 1,232 1.06 (0.98e1.15) 101,943 94,684 1.08 (1.07e1.09) 0.755
Total 15,923 14,354 1.11 (1.08e1.13) 788,014 722,337 1.09 (1.09e1.09) 0.151
CI ¼confidence interval; NA ¼not available.
a
Data retrieved from http://sowf.moi.gov.tw/stat/year/elist.htm; accessed January 15, 2012.
b
95% CI for the proportion of male births (pf) with a variance of pf (1 epf).
c
All were nonsignificant after Bonferroni correction.
574 I-W. Lee et al. / Taiwanese Journal of Obstetrics & Gynecology 51 (2012) 572e575
reporting of female births and, in some cases, even mis-
reporting of the sex [20,21]. Previous studies suggest
a growing imbalance in China’s sex ratio at birth, which is
most likely due to an increase in sex-selective abortion [20].
Contrary to China with its strict one-child policy, people in
Taiwan are encouraged to have two or more children, espe-
cially if a girl is born first. In Taiwan, the fertility rate, defined
as the number of babies born every year divided by the
number of women during childbearing age, has gradually
decreased from 7.045 in the 1940s to 1.030 in 2010 [22].In
fact, the decision by parents not to have another child if their
first child is a boy may more accurately explain the higher sex
ratio than sex-selection abortion as a result of fetal sex
detection [18]. A couple, therefore, might choose to have only
one baby if they already have a boy, whereas a couple whose
first child is a girl might attempt to have a son in the following
pregnancy [23].
Our data obtained from individuals with a cultural prefer-
ence for boys show that sex ratio is already skewed at
amniocentesis at midtrimester. The data imply that artificial
sex selection, if it were present, might occur prior to
amniocentesis.
To the best of our knowledge, no previous reports on the
prenatal human sex distribution issue have been published in
Taiwan. Our series might be the first one to investigate the sex
ratio at amniocentesis and at birth. Our data showed no
difference between the sex ratio at amniocentesis and that at
birth. However, our study had some limitations. First, the sex
ratio at birth might vary with maternal age, and the mothers in
the prenatal group at NCKUH were markedly older than the
mothers in the general population in Taiwan. Second, the
cytogenetic database does not include information on the birth
order or the sex of babies previously born in the same families.
In conclusion, we present the trends of sex ratios at the
midtrimester and at birth in Taiwan from 1992 to 2011. The
results show no difference between the sex ratios at amnio-
centesis at NCKUH and at birth in Taiwan for two decades.
From this series, we conclude that the annotation of fetal sex
by prenatal cytogenetic reports has no effect on the sex ratio at
birth. Further studies are required to draw a definite conclusion
between these links.
Acknowledgments
Special thanks to Professor Fong-Ming Chang, Department
of Obstetrics and Gynecology, National Cheng Kung Univer-
sity Hospital and College of Medicine, for his critical review
and suggestions for this manuscript.
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575I-W. Lee et al. / Taiwanese Journal of Obstetrics & Gynecology 51 (2012) 572e575
... Sex ratio, defined as the ratio of males to females in a population, is assumed to be near 1:1 [1]. Although the sex ratio of males to females in the world at birth is approximately 105:100 [2e4], in some countries, especially in Chinese society, the sex ratio of males to females was found to undergo a significant change and distortion. ...
... Some physicians and officers from the public health arena even considered the possible presence of selected abortions for female fetuses in some Asian countries, including Taiwan; therefore, it is reasonably believed that this violation of the natural sex ratio might also be present in Taiwan. To respond to this question in Taiwan, in the most recent issue of Taiwanese Journal of Obstetrics and Gynecology (Volume 51, Number 4, pages 572e575), Lee et al [1] used prenatal karyotyping results obtained during the period from 1992 to 2011 at the Cytogenetic Laboratory of the National Cheng Kung University Hospital as a study population to compare the sex ratio at birth in each year of the study period registered in the Department of Statistic, Ministry of the Interior, Administrative Yuen, Taiwan and tried to assess the difference between fetal sex ratio at a tertiary medical center and the nationwide sex ratio at birth in Taiwan [1]. The authors found that there was no significant difference in sex distribution between the National Cheng Kung University Hospital data and the nationwide data, although in a specific year, there was a significant difference between the hospital data and the nationwide data. ...
... Some physicians and officers from the public health arena even considered the possible presence of selected abortions for female fetuses in some Asian countries, including Taiwan; therefore, it is reasonably believed that this violation of the natural sex ratio might also be present in Taiwan. To respond to this question in Taiwan, in the most recent issue of Taiwanese Journal of Obstetrics and Gynecology (Volume 51, Number 4, pages 572e575), Lee et al [1] used prenatal karyotyping results obtained during the period from 1992 to 2011 at the Cytogenetic Laboratory of the National Cheng Kung University Hospital as a study population to compare the sex ratio at birth in each year of the study period registered in the Department of Statistic, Ministry of the Interior, Administrative Yuen, Taiwan and tried to assess the difference between fetal sex ratio at a tertiary medical center and the nationwide sex ratio at birth in Taiwan [1]. The authors found that there was no significant difference in sex distribution between the National Cheng Kung University Hospital data and the nationwide data, although in a specific year, there was a significant difference between the hospital data and the nationwide data. ...
... One study suggested that the maternal X-chromosome in XY embryos may result in more stable development [7]. An increasing trend in the sex ratio which indicated more male baby at birth has been noted in many countries [8], including Taiwan [9]. This study was therefore designed to determine the chromosome types of early miscarriages with or without embryonic poles and to compare the distribution of abnormalities and sex ratio in these two groups. ...
... Government statistics in Taiwan have shown a male-to-female ratio at birth of about 1.07 to 1.08. Even after excluding cultural effects, the male-to-female ratio was greater than 1.0 [9]. Skewed sex ratios have also been observed in other countries [8], suggesting that the predominance of female abortuses may be associated with early selection in utero or during embryo development. ...
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Purpose The objective of this study is to compare the chromosomal distribution of early miscarriages with or without embryonic poles. Materials and methods It was a retrospective study of 223 women who underwent dilation and curettage (D&C) between 1995 and 2013 for early miscarriages. The presence or absence of a fetal pole was evaluated by abdominal or transvaginal ultrasound. Cytogenetic tests of products of conception following culture were determined in both groups. Results Of the 223 early miscarriages, 143 had embryos and 80 did not. The abnormality rate differed significantly (61.5 % vs. 46.3 %, p
... This supports the hypothesis that sex-selective reproductive technology may play a role in the high birth sex ratio in Taiwan. Another study reported that sex distribution was consistent from mid-trimester to the time of birth, and therefore, artificial sex selection may have already occurred before the time of amniocentesis (Lee, Lai, Kuo, & Chang, 2012). This also supports the hypothesis that sex selection technology may be associated with the high sex ratio at birth in Taiwan. ...
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Chinese culture has long favored sons over daughters. With the development of reproductive technology, the methods can be used not only in facilitation of conception, but also in sex-selective termination of pregnancies. Therefore, this study aimed to investigate: (1) the rate of pregnant expectancy/planning of children; (2) whether the Chinese cultural influence of son preference still exists, and factors effecting sex preference; and (3) whether artificial reproductive technology plays a role in parents giving birth to a child of their preferred sex. We used the Taiwan Birth Cohort Study dataset at six-months, which included 21,248 babies born in 2005. More mothers than fathers reported this pregnancy as unexpected (29.0% vs. 20.5%). Over half of the parents showed no preference for the sex of their child (mothers: 52.6%, fathers: 55.8%). However, among those who showed a preference, significantly more preferred sons than daughters (son preference, mothers: 24.8%, fathers: 24.3%; daughter preference, mothers: 22.5%, fathers: 19.9%). Additionally, structural equation modeling found that parents who had planned their pregnancy were more likely to prefer sons and less likely to prefer daughters. Parents who used artificial reproductive technology for conception were more likely to prefer and conceive sons. A preference for male children still exists in Taiwan, contributing to the high sex ratio at birth of 110 in our 2005 birth cohort. However, over half of the parents reported being neutral in the preference of the gender of their offspring. This suggests that Taiwan is moving toward a more gender-equitable society.
... 14 The body of literature to date reflects mostly indirect evidence obtained by rough measurement of male:female ratios at birth in India, [15][16][17] China, 13,18,19 Vietnam 20,21 and the rest of Asia. [22][23][24][25] Prior studies of this phenomenon in industrialized countries have looked at maternal country of origin broadly but have observed it predominantly among Asian immigrants from countries where malebiased infant sex ratios have been extensively documented. 10,[26][27][28][29][30] Data on the relation between abortion practices and male:female infant ratios are lacking. ...
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Background: Skewed male:female ratios at birth have been observed among certain immigrant groups. Data on abortion practices that might help to explain these findings are lacking. Methods: We examined 1 220 933 births to women with up to 3 consecutive singleton live births between 1993 and 2012 in Ontario. Records of live births, and induced and spontaneous abortions were linked to Canadian immigration records. We determined associations of male:female infant ratios with maternal birthplace, sex of the previous living sibling(s) and prior spontaneous or induced abortions. Results: Male:female infant ratios did not appreciably depart from the normal range among Canadian-born women and most women born outside of Canada, irrespective of the sex of previous children or the characteristics of prior abortions. However, among infants of women who immigrated from India and had previously given birth to 2 girls, the overall male:female ratio was 1.96 (95% confidence interval [CI] 1.75-2.21) for the third live birth. The male:female infant ratio after 2 girls was 1.77 (95% CI 1.26-2.47) times higher if the current birth was preceded by 1 induced abortion, 2.38 (95% CI 1.44-3.94) times higher if preceded by 2 or more induced abortions and 3.88 (95% CI 2.02-7.50) times higher if the induced abortion was performed at 15 weeks or more gestation relative to no preceding abortion. Spontaneous abortions were not associated with male-biased sex ratios in subsequent births. Interpretation: High male:female ratios observed among infants born to women who immigrated from India are associated with induced abortions, especially in the second trimester of pregnancy.
... First, our study did not investigate the effects of assisted reproductive technologies. Nevertheless, there is no evidence to show any correlations of assisted reproductive technologies with the sex ratio in Taiwan [49,50]. Second, we were unable to take parental socioeconomic factors, such as educational level, into account in our analyses because the information was not available in our database. ...
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Background An extensive assessment investigating the association between sex differences and neonatal outcomes is lacking. In the current study, we estimated the correlation of gender with adverse birth outcomes in a large cohort population. Methods National population-based data containing maternal and neonatal information in 2001 to 2010 were derived from the Health Promotion Administration, Taiwan. Singletons without high-risk pregnancy were further analyzed for the sex ratio of live births in relation to neonatal outcomes—including preterm birth, birth weight, neonatal death, delivery mode, and congenital anomaly. A multivariate logistic regression model was used to adjust for possible confounders. Results In total, 2,123,100 births were valid for the analysis. Overall, the sex ratio at birth (male/female) was 1.096. Compared to multiple births, the sex ratio was significantly higher with singleton births (p < 0.001). Among multiple births, the incidence of stillbirths was significantly higher in males than in females (p < 0.05). The sex ratio at gestational age (GA) <37 weeks was 1.332, and it declined proportionally with a rise in the GA to 0.899 at GA of ≥41 weeks. In contrast, the sex ratio was 0.850 at birth weight <3000 g, and it rose proportionally with a rise in the birth weight to 1.902 at birth weight ≥4000 g (macrosomia). Operative delivery was more common in males than in females (p < 0.001). The regression analysis showed greater risks of preterm birth, macrosomia, operative delivery, neonatal death, and congenital anomaly among male newborns. Conclusions Male gender carried higher risks of adverse neonatal outcomes, including preterm birth, macrosomia, operative delivery, neonatal death, and congenital anomaly. The data have clinical implications on health surveillance for plotting strategies in response to the unbalanced sex ratio in relation to the boy preference.
... However, a study conducted in Taiwan overruled the possibility of selective abortion for the skewed SR and confirmed that the sex imbalance occurs as early as midtrimester. 5 Since disclosure of prenatal fetal sex is prohibited in Taiwan, there can be other factors that can attribute to the SR difference such as birth order, parental age, and environmental conditions. 6,7 PLBW birth is a major risk factor for infant and child mortality. ...
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Using a retrospective cohort study design, we report empirical evidence on the effect of parental socioeconomic status, primary care, and health care expenditure associated with preterm or low-birth-weight (PLBW) babies on their mortality (neonatal, postneonatal, and under-5 mortality) under a universal health care system. A total of 4668 singleton PLBW babies born in Taiwan between January 1 and December 31, 2001, are extracted from a population-based medical claims database for a follow-up of up to 5 years. Multivariate survival models suggest the positive effect of higher parental income is significant in neonatal period but diminishes in later stages. Consistent inverse relationship is observed between adequate antenatal care and the three outcomes: neonatal hazard ratio (HR) = 0.494, 95% confidence interval (CI) = 0.312 to 0.783; postneonatal HR = 0.282, 95% CI = 0.102 to 0.774; and under-5 HR = 0.575, 95% CI = 0.386 to 0.857. Primary care services uptake should be actively promoted, particularly in lower income groups, to prevent premature PLBW mortality. © 2015 APJPH.
... 10e14 The nationwide sex ratio at birth in Taiwan remained constant at 1.08 during the period from 1992 to 2011, with the highest ratio at 1.1057 in 2004 and the lowest at 1.0759 in 1993. 10 From Topçu et al's 1 study, the male-to-female sex ratio was abnormally high (1.18), compared with other countries (1.04 in the US, 1.05 in the world, and 1.08 in Taiwan), 4,11 except when compared to rural areas of China (1.20 in China). 15 Therefore, if the national sex ratio in Turkey is not 1.18, it is not appropriate to claim that Topçu et al's 1 study could be a good reference to define normal and abnormal fetal growth in newborns in Turkey. ...
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Amartya Sen first used the phrase ‘missing women’ to describe a survival disadvantage for women exposed to extreme gender discrimination in son-preference countries. In 1989 he estimated that, despite a biological survival advantage for females, there were 100 million fewer women in Asia and north Africa than expected. He blamed corrosive gender discrimination restricting the resources needed for survival. This systematic review examined demographic evidence on the impacts of profound gender discrimination on the survival of girls and women in son-preference countries. Thirty-four included studies provided consistent evidence of lower-than-expected female survival in 15 societies. Male-to-female sex ratios rose particularly in China and India between the 1980s and 2010s, despite general improvements in female mortality. High sex ratios in South Korea, however, returned to biologically normal levels. The number of ‘missing women’ rose steadily from 61 million in 1970 to 126 million in 2010 and was predicted to continue to rise until 2035. The number of ‘missing women’ in the world increased in relative and absolute terms between 1980 and 2020. Profound discrimination reduces female survival at every stage of life. Future research is needed to understand the complete pathways and mechanisms leading to poorer survival and the major policy drivers of these trends to devise the best possible ways of preventing the tragedy of ‘missing women’.
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Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex selection, in order to maximize reproductive returns. Non-human studies have provided evidence for this phenomenon, and maternal condition around the time of conception has been identified as most important factor that influence offspring sex selection. However, studies on humans have reported inconsistent results, mostly due to use of disparate measures as indicators of maternal condition. In the present study, the cross-cultural differences in human natal sex ratio were analyzed with respect to indirect measures of condition namely, life expectancy and mortality rate. Multiple regression modeling suggested that mortality rates have distinct predictive power independent of cross-cultural differences in fertility, wealth and latitude that were earlier shown to predict sex ratio at birth. These findings suggest that sex ratio variation in humans may relate to differences in parental and environmental conditions.
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High sex ratios at birth (108 boys to 100 girls or higher) are seen in China, Taiwan, South Korea and parts of India and Viet Nam. The imbalance is the result of son preference, accentuated by declining fertility. Prenatal sex detection with ultrasound followed by second trimester abortion is one of the ways sex selection manifests itself, but it is not the causative factor. Advocates and governments seeking to reverse this imbalance have largely prohibited sex detection tests and/or sex selective abortion, assuming these measures would reverse the trend. Such policies have been difficult to enforce and have met with only limited success. At the same time, such policies are starting to have adverse effects on the already limited access to safe and legal second trimester abortion for reasons other than sex selection. Moreover, the sex selection issue is being used as a platform for anti-abortion rhetoric by certain groups. Maintaining access to safe abortion and achieving a decline in high sex ratios are both important goals. Both are possible if the focus shifts to addressing the conditions that drive son preference.
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High sex ratios at birth (108 boys to 100 girls or higher) are seen in China, Taiwan, South Korea and parts of India and Viet Nam. The imbalance is the result of son preference, accentuated by declining fertility. Prenatal sex detection with ultrasound followed by second trimester abortion is one of the ways sex selection manifests itself, but it is not the causative factor. Advocates and governments seeking to reverse this imbalance have largely prohibited sex detection tests and/or sex selective abortion, assuming these measures would reverse the trend. Such policies have been difficult to enforce and have met with only limited success. At the same time, such policies are starting to have adverse effects on the already limited access to safe and legal second trimester abortion for reasons other than sex selection. Moreover, the sex selection issue is being used as a platform for anti-abortion rhetoric by certain groups. Maintaining access to safe abortion and achieving a decline in high sex ratios are both important goals. Both are possible if the focus shifts to addressing the conditions that drive son preference. Résumé Des rapports de masculinité élevés (108 garçons ou plus pour 100 filles) sont observés en Chine, à Taiwan, en République de Corée et dans des régions de l'Inde et du Viet Nam. Ce déséquilibre est le résultat de la préférence pour les enfants de sexe masculin qu'accentue la baisse de la fécondité. La détection prénatale du sexe par ultrasons suivie d'un avortement du deuxième trimestre est l'une des manifestations de la sélection du sexe du bébé, mais ce n'en est pas la cause. Habituellement, les activistes et les autorités souhaitant corriger ce déséquilibre ont interdit les tests de détection du sexe et/ou l'avortement sélectif, supposant que ces mesures renverseraient la tendance. Ces politiques ont été difficiles à appliquer et n'ont guère obtenu de résultats. En même temps, elles commencent à avoir des effets néfastes sur l'accès déjà limité à l'avortement sûr et légal du deuxième trimestre pour des raisons autres que la sélection du sexe du bébé. De plus, certains groupes opposés à l'avortement utilisent la question de la sélection du sexe comme plateforme pour leur propagande. Maintenir l'accès à un avortement médicalisé et parvenir à diminuer les rapports élevés de masculinité sont deux objectifs importants. Tous deux sont possibles en réorientant les priorités de manière à s'attaquer aux facteurs qui induisent la préférence pour les garçons. Resumen En China, Taiwán, Corea del Sur y partes de la India y Viet Nam, se ve un predominio de varones en la proporción de sexos entre recién nacidos (108 varones por 100 niñas o más). Ese desequilibrio es el resultado de la preferencia por hijos varones, acentuada por el deterioro de la fertilidad. La detección prenatal del sexo con ecografía, seguida del aborto en el segundo trimestre es una de las formas en que se manifiesta la selección del sexo, pero no son los factores causantes. Los defensores y gobiernos que buscan cambiar ese desequilibrio han prohibido en gran medida las pruebas para la detección del sexo y/o el aborto para la selección del sexo, suponiendo que estas medidas invertirían el sentido de la tendencia. Ha sido difícil hacer cumplir dichas políticas, que han tenido un éxito limitado y, al mismo tiempo, están empezando a tener efectos adversos en el acceso ya limitado al aborto seguro y legal en el segundo trimestre por motivos además de la selección del sexo. Más aún, ciertos grupos están utilizando el tema de la selección del sexo como una plataforma para la retórica anti-aborto. Mantener el acceso al aborto seguro y lograr una disminución en las altas proporciones entre sexos son ambas metas importantes. Las dos son posibles si el enfoque se dirige hacia tratar las condiciones que guían su preferencia.
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The world is currently in the midst of the greatest demographic upheaval in human history. Dramatic reductions in mortality, followed (but with a lag) by equally marked reductions in fertility, resulted in a doubling of world population between 1960 and 2000. A further increase of 2 to 4.5 billion is projected for the current half-century, with the increase concentrated in the world’s least developed countries. Despite alarmist predictions, historical increases in population have not been economically catastrophic. Moreover, changes in population age structure have opened the door to increased prosperity. Demographic changes have had and will continue to have profound repercussions for human well-being and progress, with some possibilities for mediating those repercussions through policy intervention.
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India's 2011 census revealed a growing imbalance between the numbers of girls and boys aged 0-6 years, which we postulate is due to increased prenatal sex determination with subsequent selective abortion of female fetuses. We aimed to establish the trends in sex ratio by birth order from 1990 to 2005 with three nationally representative surveys and to quantify the totals of selective abortions of girls with census cohort data. We assessed sex ratios by birth order in 0·25 million births in three rounds of the nationally representative National Family Health Survey covering the period from 1990 to 2005. We estimated totals of selective abortion of girls by assessing the birth cohorts of children aged 0-6 years in the 1991, 2001, and 2011 censuses. Our main statistic was the conditional sex ratio of second-order births after a firstborn girl and we used 3-year rolling weighted averages to test for trends, with differences between trends compared by linear regression. The conditional sex ratio for second-order births when the firstborn was a girl fell from 906 per 1000 boys (99% CI 798-1013) in 1990 to 836 (733-939) in 2005; an annual decline of 0·52% (p for trend=0·002). Declines were much greater in mothers with 10 or more years of education than in mothers with no education, and in wealthier households compared with poorer households. By contrast, we did not detect any significant declines in the sex ratio for second-order births if the firstborn was a boy, or for firstborns. Between the 2001 and 2011 censuses, more than twice the number of Indian districts (local administrative areas) showed declines in the child sex ratio as districts with no change or increases. After adjusting for excess mortality rates in girls, our estimates of number of selective abortions of girls rose from 0-2·0 million in the 1980s, to 1·2-4·1 million in the 1990s, and to 3·1-6·0 million in the 2000s. Each 1% decline in child sex ratio at ages 0-6 years implied 1·2-3·6 million more selective abortions of girls. Selective abortions of girls totalled about 4·2-12·1 million from 1980-2010, with a greater rate of increase in the 1990s than in the 2000s. Selective abortion of girls, especially for pregnancies after a firstborn girl, has increased substantially in India. Most of India's population now live in states where selective abortion of girls is common. US National Institutes of Health, Canadian Institute of Health Research, International Development Research Centre, and Li Ka Shing Knowledge Institute.
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The normal male to female livebirth sex ratio ranges from 1.03 to 1.07. Higher ratios in China, India and Korea reflect prenatal sex selection. We reviewed sex ratios for US births to investigate potential prenatal sex selection. We reviewed all US livebirths from 1975 to 2002 using National Center for Health Statistics birth certificates in 4-year intervals. We compared the sex ratios of Blacks, Chinese, Filipinos, Asian Indians and Koreans relative to Whites. We also compared the sex ratios by birth order for first, second and third and more births (third+) from 1991 to 2002. The male to female sex ratio from 1975 to 2002 was 1.053 for Whites, 1.030 (p < 0.01) for Blacks, 1.074 (p < 0.01) for Chinese and 1.073 (p < 0.01) for Filipinos. From 1991 to 2002, the sex ratio increased from 1.071 to 1.086 for Chinese, 1.060 to 1.074 for Filipinos, 1.043 to 1.087 for Asian Indians and 1.069 to 1.088 for Koreans. The highest sex ratios were seen for third+ births to Asian Indians (1.126), Chinese (1.111) and Koreans (1.109). The male to female livebirth sex ratio in the United States exceeded expected biological variation for third+ births to Chinese, Asian Indians and Koreans strongly suggesting prenatal sex selection.