Does fetal sex affect pregnancy outcome?

Fetal sex and maternal risk of gestational diabetes mellitus: the impact of having a boy

OBJECTIVE

Retrospective analyses of perinatal databases have raised the intriguing possibility of an increased risk of gestational diabetes mellitus (GDM) in women carrying a male fetus, but it has been unclear if this was a spurious association. We thus sought to evaluate the relationship between fetal sex and maternal glucose metabolism in a well-characterized cohort of women reflecting the full spectrum of gestational glucose tolerance from normal to mildly abnormal to GDM.

RESEARCH DESIGN AND METHODS

A total of 1,074 pregnant women underwent metabolic characterization, including oral glucose tolerance test (OGTT), at mean 29.5 weeks' gestation. The prevalence of GDM, its pathophysiologic determinants (β-cell function and insulin sensitivity/resistance), and its clinical risk factors were compared between women carrying a female fetus (n = 534) and those carrying a male fetus (n = 540).

RESULTS

Women carrying a male fetus had lower mean adjusted β-cell function (insulinogenic index divided by HOMA of insulin resistance: 9.4 vs. 10.5, P = 0.007) and higher mean adjusted blood glucose at 30 min (P = 0.025), 1 h (P = 0.004), and 2 h (P = 0.02) during the OGTT, as compared with those carrying a female fetus. Furthermore, women carrying a male fetus had higher odds of developing GDM (odds ratio 1.39 [95% CI 1.01-1.90]). Indeed, male fetus further increased the relative risk of GDM conferred by the classic risk factors of maternal age >35 years and nonwhite ethnicity by 47 and 51%, respectively.

CONCLUSIONS

Male fetus is associated with poorer β-cell function, higher postprandial glycemia, and an increased risk of GDM in the mother. Thus, fetal sex potentially may influence maternal glucose metabolism in pregnancy.

Combined effect of fetal sex and advanced maternal age on pregnancy outcomes

BACKGROUND

Fetal sex and maternal age are each known to affect outcomes of pregnancies. The objective of the present study was to investigate the influence of the combination of maternal age and fetal sex on pregnancy outcomes in term and post-term singleton pregnancies.

MATERIAL AND METHODS

This was a retrospective study on term singleton pregnancies delivered between 2004 and 2008 at the Chaim Sheba Medical Center. Data collected included maternal age, fetal sex, and maternal and neonatal complications. The combined effect of fetal sex and maternal age on complications of pregnancy was assessed by multivariable logistic regression models.

RESULTS

The study population comprised 37,327 pregnancies. The risk of operative deliveries increased with maternal age ≥ 40 and in pregnancies with male fetuses. The risk of maternal diabetes and of longer hospitalization increased as maternal age increased, and in women ≥ 40 carrying male fetuses. The risk of hypertensive disorders increased in pregnancies with males as maternal age advanced. The risk of shoulder dystocia and neonatal respiratory complications increased in male neonates born to women<40. The risk of neonatal hypoglycemia increased in males for all maternal ages.

CONCLUSIONS

Risk assessment for fetal sex and advanced maternal age were given for different pregnancy complications. Knowledge of fetal sex adds value to the risk assessment of pregnancies as maternal age increases.

Fetal sex modifies effects of prenatal stress exposure and adverse birth outcomes

Prenatal maternal stress is associated with pregnancy complications, poor fetal development and poor birth outcomes. Fetal sex has also been shown to affect the course of pregnancy and its outcomes. The aim of this study was to evaluate whether fetal sex modifies the association between continuous exposure to life-threatening rocket attack alarms and adverse pregnancy outcomes. A retrospective cohort study was conducted in which the exposed group was comprised of 1846 women exposed to rocket-attack alarms before and during pregnancy. The unexposed group, with similar sociodemographic characteristics, delivered during the same period of time at the same medical center, but resided out of rocket-attack range. Multivariable models for each gender separately, controlling for possible confounders, evaluated the risk associated with exposure for preterm births (PTB), low birthweight (LBW), small for gestational age and small head circumference (HC). In both univariable and multivariable analyses exposure status was a significant risk factor in female fetuses only: PTB (adj. OR = 1.43; 1.04-1.96), LBW (adj. OR = 1.41; 1.02-1.95) and HC < 31 cm (adj. OR = 1.78; 1.11-2.88). In addition, regarding all adverse outcomes, the male-to-female ratio was higher in the exposed group than in the unexposed group. The findings support the hypothesis that male and female fetuses respond differentially to chronic maternal stress.

Low Gestational Weight Gain Skews Human Sex Ratios towards Females

BACKGROUND

Human males are more vulnerable to adverse conditions than females starting early in gestation and continuing throughout life, and previous studies show that severe food restriction can influence the sex ratios of human births. It remains unclear, however, whether subtle differences in caloric intake during gestation alter survival of fetuses in a sex-specific way. I hypothesized that the ratio of male to female babies born should vary with the amount of weight gained during gestation. I predicted that women who gain low amounts of weight during gestation should produce significantly more females, and that, if gestational weight gain directly influences sex ratios, fetal losses would be more likely to be male when women gain inadequate amounts of weight during pregnancy.

METHODS

I analyzed data collected from over 68 million births over 23 years to test for a relationship between gestational weight gain and natal sex ratios, as well as between gestational weight gain and sex ratios of fetal deaths at five gestational ages.

RESULTS

Gestational weight gain and the proportion of male births were positively correlated; a lower proportion of males was produced by women who gained less weight and this strong pattern was exhibited in four human races. Further, sex ratios of fetal losses at 6 months of gestation were significantly male-biased when mothers had gained low amounts of weight during pregnancy, suggesting that low caloric intake during early fetal development can stimulate the loss of male fetuses.

CONCLUSION

My data indicate that human sex ratios change in response to resource availability via sex-specific fetal loss, and that a pivotal time for influences on male survival is early in fetal development, at 6 months of gestation.

Elevated risk of stillbirth in males: systematic review and meta-analysis of more than 30 million births

BACKGROUND

Stillbirth rates have changed little over the last decade, and a high proportion of cases are unexplained. This meta-analysis examined whether there are inequalities in stillbirth risks according to sex.

METHODS

A systematic review of the literature was conducted, and data were obtained on more than 30 million birth outcomes reported in observational studies. The pooled relative risk of stillbirth was estimated using random-effects models.

RESULTS

The crude mean rate (stillbirths/1,000 total births) was 6.23 for males and 5.74 for females. The pooled relative risk was 1.10 (95% confidence interval (CI): 1.07-1.13). The attributable fraction in the whole population was 4.2% (95% CI: 3.70-4.63), and the attributable fraction among male fetuses was 7.8% (95% CI: 7.0-8.66). Study populations from countries with known sex-biased sex selection issues had anomalous stillbirth sex ratios and higher overall stillbirth risks than other countries, reflecting increased mortality among females.

CONCLUSIONS

Risk of stillbirth in males is elevated by about 10%. The population-attributable risk is comparable to smoking and equates to approximately 100,000 stillbirths per year globally. The pattern is consistent across countries of varying incomes. Given current difficulties in reducing stillbirth rates, work to understand the causes of excess male risk is warranted. We recommend that stillbirths are routinely recorded by sex. This will also assist in exposing prenatal sex selection as elevated or equal risks of stillbirth in females would be readily apparent and could therefore be used to trigger investigation.

Cross sectional study in China: fetal gender has adverse perinatal outcomes in mainland China

Background

The association between fetal gender and pregnancy outcomes has been thoroughly demonstrated in western populations. However, this association has not been thoroughly documented in China. The primary objective of the present study is to determine whether the association of adverse pregnancy and labour outcomes with male fetuses applies to the Chinese population.

Methods

This cross-sectional hospital-based retrospective survey collected data from thirty-nine hospitals in 2011 in mainland China. A total of 109,722 women with singleton pregnancy who delivered after 28 weeks of gestation were included.

Results

Of these pregnancies, the male-to-female sex ratio was 1.2. The rates of preterm birth (7.3% for males, 6.5% for females) and fetal macrosomia (8.3% for males, 5.1% for females) were higher for male newborns, whereas fetal growth restriction (8.0% for females, 5.4% for males) and malpresentation (4.3% for females, 3.6% for males) were more frequent among female-bearing mothers. A male fetus was associated with an increased incidence of operative vaginal delivery (1.3% for males, 1.1% for females), caesarean delivery (55.0% for males, 52.9% for females), and cephalopelvic disproportion/failure to progress (10.0% for males, 9.2% for female). Male gender was also significantly associated with lower Apgar scores (<7 at 5 min, adjusted odds ratio 1.3, 95% CI 1.0-1.6), as well as a neonatal intensive care unit admission and neonatal death, even after adjustments for confounders (adjusted odds ratio 1.3, 95% CI 1.1-1.5, adjusted odds ratio 1.4, 95% CI 1.1-1.8).

Conclusion

We confirm the existence of obvious neonatal gender bias and adverse outcomes for male fetuses during pregnancy and labour in our population. Further research is required to understand the mechanisms and clinical implications of this phenomenon.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-014-0372-4) contains supplementary material, which is available to authorized users.

Maternal-fetal nutrient transport in pregnancy pathologies: the role of the placenta

Appropriate in utero growth is essential for offspring development and is a critical contributor to long-term health. Fetal growth is largely dictated by the availability of nutrients in maternal circulation and the ability of these nutrients to be transported into fetal circulation via the placenta. Substrate flux across placental gradients is dependent on the accessibility and activity of nutrient-specific transporters. Changes in the expression and activity of these transporters is implicated in cases of restricted and excessive fetal growth, and may represent a control mechanism by which fetal growth rate attempts to match availability of nutrients in maternal circulation. This review provides an overview of placenta nutrient transport with an emphasis on macro-nutrient transporters. It highlights the changes in expression and activity of these transporters associated with common pregnancy pathologies, including intrauterine growth restriction, macrosomia, diabetes and obesity, as well as the potential impact of maternal diet. Molecular signaling pathways linking maternal nutrient availability and placenta nutrient transport are discussed. How sexual dimorphism affects fetal growth strategies and the placenta’s response to an altered intrauterine environment is considered. Further knowledge in this area may be the first step in the development of targeted interventions to help optimize fetal growth.

Phenotypic differences in individuals with autism spectrum disorder born preterm and at term gestation

The objective of the study was to characterize the phenotype of males and females with autism spectrum disorder born preterm versus those born at term. Descriptive statistical analyses identified differences between male and female autism spectrum disorder subjects born preterm compared to term for several phenotypic characteristics and comorbidities. Of the 115 (13.0% of 883) born preterm, a greater percentage of males had sleep apnea (13.8% vs. 2.5%, p < 0.0001), seizure disorders (17.0% vs. 8.5%, p = 0.01), and attention-deficit/hyperactivity disorder (14.9% vs. 6.6%, p = 0.005). Females born preterm were more likely to be nonverbal (22.2% vs. 4.6%, p = 0.001). In summary, phenotypic differences were observed, especially among males. The results may have implications for understanding the underpinnings of a subset of individuals with autism spectrum disorder and contribute to the development of focused treatments for autism spectrum disorder among children born preterm.

Congenital cytomegalovirus is associated with severe forms of cerebral palsy and female sex in a retrospective population-based study

AIM

Congenital cytomegalovirus (cCMV) infection can result in poor outcomes including cerebral palsy (CP). The aim of this study was to describe the incidence and comorbidities of CP reported to the Australian Cerebral Palsy Register (ACPR) as attributed to cCMV infection.

METHOD

This was a retrospective population-based study. Cases were drawn from Australian state CP registers with population level ascertainment, 1993 to 2003 (n=2265; 56.4% males, Gross Motor Function Classification System [GMFCS] ratings available for Victorian cases only: 70% GMFCS levels I to III and 30% GMFCS levels IV to V). Clinical data were extracted and cases with cCMV reported as a known cause were compared with cases where cCMV was not reported.

RESULTS

Children with cCMV (n=34; 12 males, 22 females; mean [SD] gestational age, 36.4 wk [4.4], range 24-41 wk) accounted for 1.5% of CP cases; 2.9 per 100,000 live births, (95% confidence intervals 1.9-3.9). When compared with CP cases where cCMV was not reported, proportionally, more CP cases with cCMV were born to younger mothers (p<0.001), were female (64% vs 43%, p=0.014), had spastic quadriplegia (73% vs 21%, p<0.001), required wheeled mobility i.e. GMFCS IV or V (78% vs 28%, p<0.001), had epilepsy (70% vs 30%, p<0.001), deafness (40% vs 2%, p<0.001), functional blindness (20% vs 5%, p<0.001), and severe communication impairment (71% vs 25%, p<0.001).

INTERPRETATION

cCMV is an important potentially preventable cause of CP and is associated with severe disability and female sex in cases reported to the ACPR. Future studies utilising prospective sample collection for cCMV testing are needed to confirm these findings.

Perinatal outcome in relation to fetal sex in offspring to mothers with pre-gestational and gestational diabetes--a population-based study

AIM

The objective of the present study was to investigate if perinatal outcome differs with fetal sex in pregnancies with maternal Type 1 diabetes, Type 2 diabetes or gestational diabetes.

METHODS

This was a population-based cohort study, with data from the Medical Birth Registry in Sweden throughout the period 1998-2007. Singleton pregnancies with maternal Type 1 diabetes (n = 4092), Type 2 diabetes (n = 412) and gestational diabetes (n = 8602) were identified based on the International Classification of Diseases, 10th edition code. For comparison, 905 565 pregnancies without diabetes were included. The primary outcome was a composite outcome, consisting of any of the following diagnoses: perinatal mortality rate, major malformation, preterm delivery, acute respiratory disorders and neonatal hypoglycaemia. Logistic regression was used to obtain odds ratios for adverse outcomes in male offspring within the diabetic and reference cohorts, respectively.

RESULTS

In pregnancies with diabetes, maternal characteristics did not differ with fetal sex, except for a higher rate of Caesarean delivery in male offspring of women with Type 1 diabetes. Male infants to mothers with Type 1 diabetes and gestational diabetes had significantly increased odds of respiratory disorders [adjusted odds ratio (confidence interval) Type 1 diabetes: 1.50 (1.12-2.02); gestational diabetes: 1.81 (1.27-2.57)]. Male infants to mothers with gestational diabetes also had significantly increased odds of major malformations [adjusted odds ratio: 1.44 (1.07-1.93)]. In offspring of mothers with Type 2 diabetes, odds ratios of most outcomes were higher in male infants; however, not significantly different from female infants. In pregnancies without diabetes, male infants had significantly higher odds of all adverse outcomes, except perinatal mortality rate.

CONCLUSION

The risk of adverse perinatal outcome in offspring of mothers with Type 1 diabetes and gestational diabetes did not differ by sex, except for a higher risk in male infants for respiratory disorders. The risk of major malformations was also significantly increased in male offspring to mothers with gestational diabetes. In offspring of mothers with Type 2 diabetes, no significant differences between sexes were found.

Fetal sex-based differences in maternal hormones, angiogenic factors, and immune mediators during pregnancy and the postpartum period

Problem

Several pregnancy complications have disparities based on the sex of the fetus. It is unknown whether the sex of the fetus differentially alters the maternal immune milieu, potentially contributing to the observed differences.

Method of study

Using maternal plasma collected during 38 uncomplicated pregnancies (19 males, 19 females), we compared levels of cytokines, sex hormones, and angiogenic factors throughout gestation and postpartum.

Results

Male fetal sex was associated with higher levels of proinflammatory cytokines (G-CSF, IL-12p70, IL-21, and IL-33) and angiogenic factors (PlGF and VEGF-A) compared with female fetal sex at multiple timepoints. Female fetal sex was associated with higher levels of regulatory cytokines (IL-5, IL-9, IL-17, and IL-25). IL-27 increased throughout pregnancy regardless of fetal sex. There was no fetal sex-based difference in analyte concentrations at the postpartum measurement.

Conclusion

Women carrying a male fetus exhibit a more proinflammatory/proangiogenic immune milieu than women carrying a female fetus.

Integrative transcriptome meta-analysis reveals widespread sex-biased gene expression at the human fetal-maternal interface

As males and females share highly similar genomes, the regulation of many sexually dimorphic traits is constrained to occur through sex-biased gene regulation. There is strong evidence that human males and females differ in terms of growth and development in utero and that these divergent growth strategies appear to place males at increased risk when in sub-optimal conditions. Since the placenta is the interface of maternal-fetal exchange throughout pregnancy, these developmental differences are most likely orchestrated by differential placental function. To date, progress in this field has been hampered by a lack of genome-wide information on sex differences in placental gene expression. Therefore, our motivation in this study was to characterize sex-biased gene expression in the human placenta. We obtained gene expression data for >300 non-pathological placenta samples from 11 microarray datasets and applied mapping-based array probe re-annotation and inverse-variance meta-analysis methods which showed that >140 genes (false discovery rate (FDR) <0.05) are differentially expressed between male and female placentae. A majority of these genes (>60%) are autosomal, many of which are involved in high-level regulatory processes such as gene transcription, cell growth and proliferation and hormonal function. Of particular interest, we detected higher female expression from all seven genes in the LHB-CGB cluster, which includes genes involved in placental development, the maintenance of pregnancy and maternal immune tolerance of the conceptus. These results demonstrate that sex-biased gene expression in the normal human placenta occurs across the genome and includes genes that are central to growth, development and the maintenance of pregnancy.

Prenatal and perinatal risk factors in a twin study of autism spectrum disorders

INTRODUCTION

Multiple studies associate prenatal and perinatal complications with increased risks for autism spectrum disorders (ASDs). The objectives of this study were to utilize a twin study design to 1) Investigate whether shared gestational and perinatal factors increase concordance for ASDs in twins, 2) Determine whether individual neonatal factors are associated with the presence of ASDs in twins, and 3) Explore whether associated factors may influence males and females differently.

METHODS

Data from medical records and parent response questionnaires from 194 twin pairs, in which at least one twin had an ASD, were analyzed.

RESULTS

Shared factors including parental age, prenatal use of medications, uterine bleeding, and prematurity did not increase concordance risks for ASDs in twins. Among the individual factors, respiratory distress demonstrated the strongest association with increased risk for ASDs in the group as a whole (OR 2.11, 95% CI 1.27-3.51). Furthermore, respiratory distress (OR 2.29, 95% CI 1.12-4.67) and other markers of hypoxia (OR 1.99, 95% CI 1.04-3.80) were associated with increased risks for ASDs in males, while jaundice was associated with an increased risk for ASDs in females (OR 2.94, 95% CI 1.28-6.74).

CONCLUSIONS

Perinatal factors associated with respiratory distress and other markers of hypoxia appear to increase risk for autism in a subgroup of twins. Future studies examining potential gender differences and additional prenatal, perinatal and postnatal environmental factors are required for elucidating the etiology of ASDs and suggesting new methods for treatment and prevention.

Inverse relationship between gestational weight gain and glucose uptake in human placenta from female foetuses

BACKGROUND

Maternal obesity and gestational weight gain (GWG) have a significant impact on the in utero environment, and thus on foetal development and the health of the offspring later in life.

OBJECTIVE

The aim of this study was to determine the effect of maternal pre-existing obesity and maternal GWG on glucose uptake from placentas from male and female offspring.

METHODS

Total glucose uptake was measured in placental explants using radio-labelled glucose.

RESULTS

In the female placentas (n = 36), GWG and glucose uptake were significantly negatively correlated (r = -0.7, P < 0.0001; n = 36), and customized birthweight centile correlated with placental glucose uptake (r = 0.36, P = 0.03) but not GWG. In the male placentas (n = 45), GWG and glucose uptake were not related, and customized birthweight centile correlated with GWG (r = 0.34, P = 0.02; n = 45), but not placental glucose uptake.

CONCLUSIONS

The female placenta can adapt glucose uptake in the face of excessive GWG. The male placenta showed no evidence of changing glucose uptake in response to maternal GWG.

Medical and sociodemographic risk factors for preterm birth in a French Caribbean population of African descent

There appears to be an incompressible high rate of preterm births among populations of African origin irrespective of their geographic location. The objective of this study was to assess the risk factors for preterm birth in a French Caribbean population of African descent, offered medical care comparable to that on the French mainland, but presenting a higher rate of preterm birth. The study was based on a birth cohort at maternity hospitals in Guadeloupe (French West Indies) including 911 singleton pregnancies enrolled during their third trimester check-up visits. Associations between risk factors and the risk of preterm delivery (spontaneous and induced) were assessed using a multivariate Cox model. In addition, prevalences of sociodemographic and medical factors in Guadeloupe were compared with those on the French mainland. 144 women (15.8 %) delivered preterm, medically induced in 52 %. Women delivering preterm were more often over 35 years old (37 %), single (54 %), and had higher prevalence of prior preterm birth (20 %), prior miscarriage (37 %), lupus (3 %), asthma (14 %), gestational hypertension (26 %), gestational diabetes (13 %) and urinary tract infection (24 %) than women with term births. In the whole cohort, these risk factors were also more frequent than in mainland France. Our results suggest highly prevalent medical risk factors for preterm births in Guadeloupe. This observation combined with specific social risk factors (older maternal age, single living) less frequent on the French mainland probably explains a large part of a higher prevalence of preterm births in this population despite similar medical provision.

Snoring during pregnancy and its relation to sleepiness and pregnancy outcome - a prospective study

BACKGROUND

The incidence of snoring and sleepiness is known to increase during pregnancy, and this might impact maternal health and obstetric outcome. However, the association between snoring and sleepiness during pregnancy is not fully understood. This study was aimed at investigating the development of snoring during pregnancy and prospectively assessing if there is an association between snoring and sleepiness or adverse pregnancy outcomes, such as preeclampsia, mode of delivery, and fetal complications.

METHODS

Consecutively recruited pregnant women (n = 500) received a questionnaire concerning snoring and sleep at the 1st and 3rd trimester of pregnancy. The women who had rated their frequency of snoring at both occasions (n = 340) were divided into subgroups according to the development of snoring they reported and included in the subsequent analyses. Additional medical data were collected from the medical records.

RESULTS

The frequency of snoring was 7.9% in the 1st trimester and increased to 21.2% in the 3rd trimester of pregnancy. The women who snored already in early pregnancy had significantly higher baseline BMI (p = 0.001) than the women who never snored, but snoring was not associated with the magnitude of weight gain during pregnancy. Snoring women were more likely to experience edema in late pregnancy than the non-snorers. Women who started to snore during pregnancy had higher Epworth Sleepiness Scores than the non snorers in both early and late pregnancy. No significant association between obstetric outcome and snoring was found.

CONCLUSION

Snoring does increase during pregnancy, and this increase is associated with sleepiness, higher BMI at the start of pregnancy and higher prevalence of edema, but not with weight gain.

Changes in spectral power of fetal heart rate variability in small-for-gestational-age fetuses are associated with fetal sex

BACKGROUND

Little is known about the influences of fetal weight and sex on spectral analysis of fetal heart rate (FHR) variability.

AIM

The study aims to assess whether there are differences in spectral power of FHR variability according to fetal weight and sex during labor.

STUDY DESIGN

Case-control study. A total of 414 singleton term deliveries without fetal acidemia were divided into small-for-gestational-age (SGA) (n=29) and non-SGA (n=385) groups. Analyses were performed separately according to fetal sex.

SUBJECTS

FHR recordings obtained with cardiotocography during the last 2h of labor preceding delivery.

OUTCOME MEASURES

Our outcome measures include spectral power of FHR variability.

RESULTS

For the male group, SGA fetuses had significantly lower values for low, movement, high, and total frequencies of spectral power compared with non-SGA fetuses (all P<0.005). Normalized low frequency (LFn) was significantly higher, and normalized high frequency (HFn) was significantly lower in SGA fetuses compared with non-SGA fetuses (all P<0.005). In contrast, for the female group, there were no significant differences in any of the indices of spectral power between the SGA and non-SGA fetuses. In addition, SGA males had significantly higher LFn spectral power and lower HFn spectral power compared to SGA females (P=0.016, and 0.041, respectively).

CONCLUSIONS

SGA males have decreased spectral power of FHR variability compared with non-SGA males during labor. However, there are no differences between SGA and non-SGA female fetuses. It is important in the clinical setting to take fetal weight and sex into account during FHR monitoring using spectral analysis.

Sex-related growth differences are present but not enhanced in in vitro fertilization pregnancies

OBJECTIVE

To determine whether IVF modifies the effect of fetal sex on growth.

DESIGN

Retrospective cohort study.

SETTING

Tertiary care center and related facilities.

PATIENT(S)

Singleton live births without fetal/maternal comorbidities from fertile women who conceived without the use of assisted reproductive technologies and infertile women who conceived with IVF.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The primary outcome was birth weight (BW). Secondary outcomes were fetal crown-rump length (CRL) in the first trimester, biparietal diameter (BPD), and estimated fetal weight (EFW) in the second trimester.

RESULT(S)

There were no differences in baseline characteristics between women carrying male fetuses and those carrying female fetuses in either mode of conception. In unadjusted analyses, the male-female differentials in fetal BPD and BW were more pronounced in the IVF cohort than in the unassisted cohort. In multivariable regression analysis, male BPD exceeded female BPD by 0.12 cm, male EFW exceeded female EFW by 12 g, and male BW exceeded female BW by 172 g. IVF did not have a significant effect on BPD but was associated with a 52 g increase in EFW in the midgestation. IVF was associated with an 81-g reduction in BW. IVF did not modify the magnitude of size differences between the sexes in the midgestation or at birth.

CONCLUSION(S)

Comparable sex-dependent differential growth occurs in unassisted and IVF pregnancies.

Expression of the placental transcriptome in maternal nutrient reduction in baboons is dependent on fetal sex

Maternal undernutrition increases the risk of perinatal complications and predisposes offspring to obesity, diabetes, and cardiovascular disease later in life. Emerging evidence suggests that changes in placental function play a role in linking altered maternal nutrition in pregnancy to the subsequent development of adult disease. The susceptibility for disease in response to an adverse intrauterine environment differs distinctly between boys and girls, with girls typically having better outcomes. Here, we tested the hypothesis that regulation of the placental transcriptome by maternal nutrient reduction (NR) is dependent on fetal sex. We used a nonhuman primate model of NR in which maternal global food intake was reduced by 30% in baboons starting at gestational day (GD) 30. At GD 165 (term = GD 183), placental genome expression profiling of 6 control (n = 3 females, 3 males) and 6 nutrient restricted (n = 3 females, 3 males) fetuses was carried out followed by bioinformatic analysis. Surprisingly, there was no coordinated placental molecular response to decreased nutrient availability when analyzing the data without accounting for fetal sex. In contrast, female placentas exhibited a highly coordinated response that included upregulation of genes in networks, pathways, and functional groups related to programmed cell death and downregulation of genes in networks, pathways, and functional groups associated with cell proliferation. These changes were not apparent in the male placentas. Our data support the concept that female placentas initiate complex adaptive responses to an adverse intrauterine environment, which may contribute to increased survival and better pregnancy outcomes in girls.

The human placental sexome differs between trophoblast epithelium and villous vessel endothelium

Molecular mechanisms underlying sexual dimorphism in mammals, fetal sex influences on intrauterine development, and the sex-biased susceptibility for selected diseases in adulthood are novel areas of current research. As importantly, two decades of multifaceted research has established that susceptibility to many adult disorders originates in utero, commonly secondary to the effects of placental dysfunction. We hypothesized that fetal sex influences gene expression and produces functional differences in human placentas. We thus extended previous studies on sexual dimorphism in mammals, which used RNA isolated from whole tissues, to investigate the effects of sex on four cell-phenotypes within a single key tissue, human placental villi. The cells studied included cytotrophoblasts, syncytiotrophoblast, arterial and venous endothelial cells. The cells were isolated from placentas of male or female fetuses and subjected to microarray analysis. We found that fetal sex differentially affected gene expression in a cell-phenotype dependent manner among all four cell-phenotypes. The markedly enriched pathways in males were identified to be signaling pathways for graft-versus-host disease as well as the immune and inflammatory systems that parallel the reported poorer outcome of male fetuses. Our study is the first to compare global gene expression by microarray analysis in purified, characterized, somatic cells from a single human tissue, i.e. placental villi. Importantly, our findings demonstrate that there are cell-phenotype specific, and tissue-specific, sex-biased responses in the human placenta, suggesting fetal sex should be considered as an independent variable in gene expression analysis of human placental villi.

Imprinted and X-linked non-coding RNAs as potential regulators of human placental function

Pregnancy outcome is inextricably linked to placental development, which is strictly controlled temporally and spatially through mechanisms that are only partially understood. However, increasing evidence suggests non-coding RNAs (ncRNAs) direct and regulate a considerable number of biological processes and therefore may constitute a previously hidden layer of regulatory information in the placenta. Many ncRNAs, including both microRNAs and long non-coding transcripts, show almost exclusive or predominant expression in the placenta compared with other somatic tissues and display altered expression patterns in placentas from complicated pregnancies. In this review, we explore the results of recent genome-scale and single gene expression studies using human placental tissue, but include studies in the mouse where human data are lacking. Our review focuses on the ncRNAs epigenetically regulated through genomic imprinting or X-chromosome inactivation and includes recent evidence surrounding the H19 lincRNA, the imprinted C19MC cluster microRNAs, and X-linked miRNAs associated with pregnancy complications.

Gender-specific heart rate dynamics in severe intrauterine growth-restricted fetuses

BACKGROUND

Management of intrauterine growth restriction (IUGR) remains a major issue in perinatology.

AIMS

The objective of this paper was the assessment of gender-specific fetal heart rate (FHR) dynamics as a diagnostic tool in severe IUGR.

SUBJECTS

FHR was analyzed in the antepartum period in 15 severe IUGR fetuses and 18 controls, matched for gestational age, in relation to fetal gender.

OUTCOME MEASURES

Linear and entropy methods, such as mean FHR (mFHR), low (LF), high (HF) and movement frequency (MF), approximate, sample and multiscale entropy. Sensitivities and specificities were estimated using Fisher linear discriminant analysis and the leave-one-out method.

RESULTS

Overall, IUGR fetuses presented significantly lower mFHR and entropy compared with controls. However, gender-specific analysis showed that significantly lower mFHR was only evident in IUGR males and lower entropy in IUGR females. In addition, lower LF/(MF+HF) was patent in IUGR females compared with controls, but not in males. Rather high sensitivities and specificities were achieved in the detection of the FHR recordings related with IUGR male fetuses, when gender-specific analysis was performed at gestational ages less than 34 weeks.

CONCLUSIONS

Severe IUGR fetuses present gender-specific linear and entropy FHR changes, compared with controls, characterized by a significantly lower entropy and sympathetic-vagal balance in females than in males. These findings need to be considered in order to achieve better diagnostic results.

Placental oleic acid uptake is lower in male offspring of obese women

INTRODUCTION

The fetus is dependent on the placenta for its supply of long chain polyunsaturated fatty acids (LCPUFA), which are essential in fetal growth and development. Previous work suggests that high maternal body mass index (BMI) inhibits fetal LCPUFA delivery and males have greater fatty acid requirements than females during development. We hypothesized that male placental fatty acid uptake would be more sensitive to maternal BMI compared to females.

METHODS

Term placental samples were collected from healthy women receiving Cesarean section (n = 38). Placental fatty acid transporter and binding protein gene expression and uptake of oleic acid (OA), arachidonic acid, (AA) and docosahexanoic acid (DHA) were measured. Two-way ANOVA was used to assess the effects of fetal sex and maternal overweight/obesity (BMI >26 kg/m2).

RESULTS

Placental fatty acid uptake of OA was 43% lower in male offspring and 73% higher in female offspring of obese compared to normal BMI women (P < 0.05). The interaction between fetal sex and maternal BMI had a significant effect on both OA (P = 0.002) and AA uptake (P = 0.01). DHA uptake was not affected by fetal sex or maternal obesity. Placental fatty acid transporter CD36 and binding protein FABP5 gene expression levels were lower in male offspring of obese mothers but were not affected by BMI among females.

CONCLUSION

Maternal obesity and fetal sex significantly affect the placental uptake of oleate and arachidonate. Placental fatty acid uptake in both male and female fetuses is sensitive to maternal BMI, but males may have inadequate acquisition of the unsaturated fatty acid OA, when exposed to maternal obesity.

"Trophoblast islands of the chorionic connective tissue" (TICCT): a novel placental histologic feature

INTRODUCTION

We found isolated or clustered trophoblasts in the chorionic connective tissue of the extraplacental membranes, and defined this novel histologic feature as the "trophoblast islands of the chorionic connective tissue" (TICCT). This study was conducted to determine the clinical significance of TICCT.

METHODS

Immunohistochemistry for cytokeratin-7 was performed on the chorioamniotic membranes (N = 2155) obtained from singleton pregnancies of 1199 uncomplicated term and 956 preterm deliveries. The study groups comprised 1236 African-American and 919 Hispanic women. Gestational age ranged from 24(+0) weeks to 41(+6) weeks. Multiple logistic regression analysis was performed to investigate the magnitude of association between patient characteristics and the presence of TICCT.

RESULTS

The likelihood of TICCT was significantly associated with advancing gestational age both in term (OR: 1.29, 95% CI: 1.16-1.45, p < 0.001) and preterm deliveries (OR: 1.19, 95% CI: 1.07-1.32, p = 0.001) . Hispanic women were less likely than African-American women to have TICCT across gestation in term (OR: 0.23, 95% CI: 0.18-0.31, p < 0.001) and preterm pregnancies (OR: 0.41, 95% CI: 0.29-0.58, p < 0.001). Women with a female fetus were significantly more likely to have TICCT than women with a male fetus, in both term (OR: 1.64, 95% CI: 1.28-2.11, p < 0.001) and preterm gestations (OR: 2.04, 95% CI: 1.46-2.85, p < 0.001). TICCT was 40% less frequent in the presence of chronic placental inflammation [term (OR: 0.60, 95% CI: 0.45-0.81, p = 0.001) and preterm gestations (OR: 0.58, 95% CI: 0.40-0.84, p = 0.003)] and in parous women at term (OR: 0.60, 95% CI: 0.44-0.81, p = 0.001).

CONCLUSIONS

Our findings suggest that the duration of pregnancy, fetal sex, and parity may influence the behavior of extravillous trophoblast and placental mesenchymal cells.

Fetal gender and pregnancy outcomes in Libya: a retrospective study

Objective

The relationship between pregnancy outcomes and fetal gender is well reported from different areas in the world, but not from Africa. In this study, we try to understand whether the recorded phenomenon of association of adverse pregnancy outcomes with a male fetus applies to our population.

Materials and methods

A total of 29,140 patient records from 2009 and 2010 were retrieved from Aljalaa Maternity Hospital, Tripoli, Libya. Analysis was carried out to find the correlation between fetal gender and different pregnancy outcomes.

Results

A male fetus was associated with an increased incidence of gestational diabetes mellitus (odds risk 1.4), preterm delivery (6.7% for males, 5.5% for females, odds risk 1.24), cesarean section (23.9% for males, 20% for females, odds risk 1.25), and instrumental vaginal delivery (4.4% for males, 3.1% for females, odds risk 1.48), p<0.005. Preeclampsia was more frequent among preterm females and postterm males, p<0.005. It was also more frequent in male-bearing primigravids, p<0.01.

Conclusion

We confirm the existence of an adverse effect of a male fetus on pregnancy and labor in our population. We recommend further research to understand the mechanisms and clinical implications of this phenomenon.

Sex differences in developmental programming models

The theory of developmental programming suggests that diseases such as the metabolic syndrome may be ‘programmed’ by exposure to adverse stimuli during early development. The developmental programming literature encompasses the study of a wide range of suboptimal intrauterine environments in a variety of species and correlates these with diverse phenotypic outcomes in the offspring. At a molecular level, a large number of variables have been measured and suggested as the basis of the programmed phenotype. The range of both dependent and independent variables studied often makes the developmental programming literature complex to interpret and the drawing of definitive conclusions difficult. A common, though under-explored, theme of many developmental programming models is a sex difference in offspring outcomes. This holds true across a range of interventions, including dietary, hypoxic, and surgical models. The molecular and phenotypic outcomes of adversein uteroconditions are often more prominent in male than female offspring, although there is little consideration given to the basis for this observation in most studies. We review the evidence that maternal energy investment in male and female conceptuses may not be equal and may be environment dependent. It is suggested that male and female development could be viewed as separate processes from the time of conception, with differences in both timing and outcomes.

Fetal sex and preterm birth

Rates of preterm birth vary between different populations and ethnic groups. Epidemiologic studies have suggested that the incidence of preterm birth is also higher in pregnancies carrying a male fetus; the male:female difference is greater in earlier preterm pregnancy. Placental or chorion trophoblast cells from pregnancies with a male fetus produced more pro-inflammatory TNFα in response to LPS stimulation and less anti-inflammatory IL-10 and granulocyte colony stimulating factor (G-CSF) than cells from pregnancies with a female fetus, more prostaglandin synthase (PTGS-2) and less prostaglandin dehydrogenase (PGDH). These results suggest that in the presence of a male fetus the trophoblast has the potential to generate a more pro-inflammatory environment. Maturation of the fetal hypothalamic-pituitary-adrenal axis and expression of placental genes, particularly 11β hydroxysteroid dehydrogenase-2 are also expressed in a sex dependent manner, consistent with the sex-biasing influences on gene networks. Sex differences in these activities may affect clinical outcomes of pre- and post-dates pregnancies and fetal/newborn wellbeing. These factors need consideration in studies of placental function and in the development of personalized strategies for the diagnosis of preterm labor and postnatal health.

The effects of estrogen in ischemic stroke

Stroke is a leading cause of death and the most common cause of long-term disability in the USA. Women have a lower incidence of stroke compared with men throughout most of the lifespan which has been ascribed to protective effects of gonadal steroids, most notably estrogen. Due to the lower stroke incidence observed in pre-menopausal women and robust preclinical evidence of neuroprotective and anti-inflammatory properties of estrogen, researchers have focused on the potential benefits of hormones to reduce ischemic brain injury. However, as women age, they are disproportionately affected by stroke, coincident with the loss of estrogen with menopause. The risk of stroke in elderly women exceeds that of men and it is clear that in some settings estrogen can have pro-inflammatory effects. This review will focus on estrogen and inflammation and its interaction with aging.

A potential novel spontaneous preterm birth gene, AR, identified by linkage and association analysis of X chromosomal markers

Preterm birth is the major cause of neonatal mortality and morbidity. In many cases, it has severe life-long consequences for the health and neurological development of the newborn child. More than 50% of all preterm births are spontaneous, and currently there is no effective prevention. Several studies suggest that genetic factors play a role in spontaneous preterm birth (SPTB). However, its genetic background is insufficiently characterized. The aim of the present study was to perform a linkage analysis of X chromosomal markers in SPTB in large northern Finnish families with recurrent SPTBs. We found a significant linkage signal (HLOD  = 3.72) on chromosome locus Xq13.1 when the studied phenotype was being born preterm. There were no significant linkage signals when the studied phenotype was giving preterm deliveries. Two functional candidate genes, those encoding the androgen receptor (AR) and the interleukin-2 receptor gamma subunit (IL2RG), located near this locus were analyzed as candidates for SPTB in subsequent case-control association analyses. Nine single-nucleotide polymorphisms (SNPs) within these genes and an AR exon-1 CAG repeat, which was previously demonstrated to be functionally significant, were analyzed in mothers with preterm delivery (n = 272) and their offspring (n = 269), and in mothers with exclusively term deliveries (n = 201) and their offspring (n = 199), all originating from northern Finland. A replication study population consisting of individuals born preterm (n = 111) and term (n = 197) from southern Finland was also analyzed. Long AR CAG repeats (≥26) were overrepresented and short repeats (≤19) underrepresented in individuals born preterm compared to those born at term. Thus, our linkage and association results emphasize the role of the fetal genome in genetic predisposition to SPTB and implicate AR as a potential novel fetal susceptibility gene for SPTB.

Breastfeeding and early brain development: the Generation R study

Breastfeeding during infancy is associated with a range of short- and long-term health benefits. We examine whether breastfeeding in the first 2 months of life is associated with structural markers of brain development in infants from the general population. This study was embedded within the Generation R study. Cranial ultrasounds were obtained at approximately 7 weeks post-natal age. The diameter of the gangliothalamic ovoid, corpus callosum length, ventricular volume and head circumference were measured. Maternal reports of breastfeeding were obtained at 2 months of age. We examined associations in relation to current breastfeeding practices (exclusively breastfed, n = 318, breast- and bottle-fed, n = 119, and bottle-fed, n = 243). Analyses were adjusted for head size and relevant covariates. Secondary analyses were conducted for breastfeeding history (exclusively breastfed, n = 318, breast- and bottle-fed, n = 281, and never breastfed, n = 81). Exclusive breastfeeding was associated with more optimal brain development compared with babies who were bottle-fed or never breastfed. Results were most consistent for gangliothalamic ovoid diameter. Larger gangliothalamic ovoid diameters were evident in babies who were exclusively breastfed compared with bottle-fed babies [difference between means (95% confidence interval) = 0.21(0.02, 0.39), P = 0.02]. Smaller ventricular volume and larger head circumference were also found for exclusively breastfed babies. Breastfeeding was not significantly associated with corpus callosum length. Maternal reports of breastfeeding are associated with more mature brain development within the first 2 months of life. Results are most consistent for gangliothalamic ovoid diameter, a subcortical structure rich in docosahexaenoic acid. Findings also pointed to non-specific neural developmental advantage for exclusively breastfed babies.

Occurrence of fetal macrosomia rate and its maternal and neonatal complications: a 5-year cohort study

Background. Macrosomia is defined as an infant's birth weight of more than 4000 g at term which is to different maternal and neonatal complications. Several studies have been done on factors influencing risk of macrosomia, but there is lack of information and study in our country regarding macrosomia complications. Objective. The aim of this study was to determine the prevalence of macrosomia and its complications. Method. A cohort study was conducted from 2007 to 2011 at Obstetrics and Gynecology Department, Razi Hospital in Ahvaz city, Iran. All pregnant mothers who were referred to Obstetrics and Gynecology Department for delivery were included in this study. The total number of 201,102 pregnant mothers was recruited and divided into case and control groups after delivery (macrosomia (case) and normal weight infants (control) groups). Results. Out of total deliveries (201,102), there were 1800 macrosomia, (9%). Gestational diabetes, maternal obesity (BMI), maternal aged and positive history of previous macrosomia were the major risk factors for macrosomia which were compared with the normal weight infant groups (P < 0.001 for all parameters). Neonatal complications associated with macrosomia included humerus—clavicle fractures and arm—brachial plexus injury which were significant compared to the control group (P < 0.001 for all parameters). Conclusion. The macrosomia is potentially dangerous for the mother and the neonate. It is important to recognize the suspected fetal macrosomia to prevent its risk factors and complications. There is a need to provide all delivery facilities and care services to prevent and reduce the maternal and neonatal macrosomia complications.

Infant and fetal mortality among a high fertility and mortality population in the Bolivian Amazon

Indigenous populations experience higher rates of poverty, disease and mortality than non-indigenous populations. To gauge current and future risks among Tsimane Amerindians of Bolivia, I assess mortality rates and growth early in life, and changes in risks due to modernization, based on demographic interviews conducted Sept. 2002-July 2005. Tsimane have high fertility (total fertility rate = 9) and infant mortality (13%). Infections are the leading cause of infant death (55%). Infant mortality is greatest among women who are young, monolingual, space births close together, and live far from town. Infant mortality declined during the period 1990-2002, and a higher rate of reported miscarriages occurred during the 1950-1989 period. Infant deaths are more frequent among those born in the wet season. Infant stunting, underweight and wasting are common (34%, 15% and 12%, respectively) and greatest for low-weight mothers and high parity infants. Regression analysis of infant growth shows minimal regional differences in anthropometrics but greater stunting and underweight during the first two years of life. Males are more likely to be underweight, wasted, and spontaneously aborted. Whereas morbidity and stunting are prevalent in infancy, greater food availability later in life has not yet resulted in chronic diseases (e.g. hypertension, atherosclerosis and diabetes) in adulthood due to the relatively traditional Tsimane lifestyle.

Sex-specific basis of severe placental dysfunction leading to extreme preterm delivery

OBJECTIVES

Since pregnancies with a male fetus have higher perinatal complications attributed to placental dysfunction, including severe pre-eclampsia and intrauterine growth restriction, the objective of our study was to formally evaluate placental pathology for a placental origin of these sex-specific differences.

DESIGN

Retrospective study at Mount Sinai Hospital in Toronto, Canada. Identification of 262 singleton pregnancies affected by severe pre-eclampsia and/or intrauterine growth restriction who delivered between 22 and 32 weeks' gestation from 2000 to 2010. Detailed placental pathology was reviewed, and data from 140 pregnancies with male fetuses were compared with 122 pregnancies with female fetuses. A comparison group of 40 unaffected pregnancies who delivered in the same gestational range was used to determine baseline rates of placental pathology.

MAIN OUTCOME MEASURED

Detailed placental pathology, including placental development/differentiation, velamentous umbilical cord insertion, maternal-fetal interface pathology, villous infarction, hemorrhagic lesions, villous development, and fetal vascular under-perfusion.

RESULTS

Impaired placental development and differentiation was equally common amongst males (73/140, 52.1%) and females (69/122, 56.6%). Male placentas exhibited significantly higher rates of chronic deciduitis (17.9% vs. 9.0%; relative risk [RR] 1.98, 95% confidence interval [CI] 1.02-3.86) and velamentous umbilical cord insertion (9.5% vs. 1.7%; RR 5.66, 95% CI 1.30-24.6), and a significantly lower frequency of villous infarction (55.4% vs. 73.7%; RR 0.75, 95% CI 0.62-0.90) than female placentas. No significant differences were noted for other lesions.

CONCLUSIONS

Fetal sex exerts a differential effect on the placental pathology that mediates severe pre-eclampsia and/or IUGR. Placental pathology at birth may provide insight into the mechanisms linking adverse in utero events with long-term adult disease since, for example, a male tendency to an inflammatory pathology at the maternal-fetal interface may be linked to the excess risk of coronary artery disease.

A nationwide survey of risk factors for stillbirth in Taiwan, 2001-2004

OBJECTIVE

The purpose of this study was to evaluate the nationwide stillbirth rate and explore the potential risk factors associated with stillbirths.

PATIENTS AND METHODS

Data from vital registrations during the time period from January 1, 2001 through to December 31, 2004 in Taiwan were used. Stillbirth was defined as fetal death with more than 20 completed weeks' gestational age (GA) or with birth weight more than 500 g if the GA was not known.

RESULTS

There were a total of 8481 stillbirths identified nationwide between January 1, 2001 and December 31, 2004. The stillbirth rate was nine per 1000 total births in the study period, and the proportionate decline was nearly 48.8% in the most recent decade. There was a significant increase in average maternal age during this period. Advanced maternal age and teenage pregnancy were independent significant risk factors for stillbirths even after accounting for the effects of medical conditions that were more likely to occur among these particular age groups. Those fetuses that had been exposed to cord prolapse, maternal cervical incompetence and oligohydramnios/polyhydramnios were especially vulnerable. By contrast, women who had foreign nationality, fetal ultrasound surveys, fetal heart beat monitoring and hastened parturition were less likely to have stillbirth.

CONCLUSION

The stillbirth rate in Taiwan has remained high despite advancements in medical care. Prenatal evaluation of high risk women may decrease the adverse fetal outcomes.

Impact of fetal gender on the labor curve

OBJECTIVE

We sought to estimate the association between fetal gender and first-stage labor curve at term.

STUDY DESIGN

Within a large, retrospective cohort study of consecutive, singleton term labor patients who delivered in the second stage, we compared the active phase of first-stage labor by fetal gender. The primary outcome was length of active stage 1. Interval-censored regression was used to estimate the effect of fetal gender on the duration of active first stage (4-10 cm) and was adjusted for relevant covariates.

RESULTS

Of 2400 women, 2373 women had complete labor information and were available for this analysis. Male gender was associated with both a statistically significantly longer active first stage of labor (4.6 vs 4.0 hours; P = .002) and stratified analyses by parity and labor type.

CONCLUSION

Male fetuses are associated with longer active phase of the first stage of labor and, specifically, may need to be considered in the setting of arrest diagnoses.

Male sex bias in placental dysfunction

Several reports suggest a male fetal preponderance in a variety of complications of pregnancy attributable to severe placental dysfunction (SPD). However, the underlying mechanisms remain unknown. Our primary objective was to explore the relationship between fetal sex and the spectrum of conditions implicated in abnormal placentation. We identified singleton pregnancies with a fetus delivered between 20 + 0 and 32 + 6 weeks of gestation with one or more pregnancy complications attributed to SPD (severe pre-eclampsia, intra-uterine fetal death, intra-uterine growth restriction, abnormal Doppler studies, abruption) at a single institution between 1999 and 2007. Pedigrees of index cases were created to define the relationship between fetal sex and the risk of SPD. We identified 132 index cases, 97/132 (73%) were male. Eighty-four index cases had a total of 133 sibs, of which 37/133 (28%) were affected with SPD (22 male, 15 female). A male sex preponderance persisted across all manifestations of PD in index cases with sibs. In families with the absence of maternal chronic hypertension (cHTN; n = 70), the index case was 5.9 (95% CI 2.28-16.15; P <0.001) times more likely to be male and most (12/14) affected sibs of male index cases were male, while female index cases had no affected sibs. Our results confirm a male fetal sex preponderance in SPD. In a subgroup analysis of families without cHTN, a significant male bias was found to extend to sibs of index cases. This suggests a potential genetic mechanism predisposing the male fetus to abnormal placental development.

Fetal sex affects expression of renin-angiotensin system components in term human decidua

The maternal decidua expresses the genes of the renin-angiotensin system (RAS). Human decidua was collected at term either before labor (i.e. cesarean delivery) or after spontaneous labor. The mRNA for prorenin (REN), prorenin receptor (ATP6AP2), angiotensinogen (AGT), angiotensin-converting enzymes 1 and 2 (ACE1 and ACE2), angiotensin II type 1 receptor (AGTR1), and angiotensin 1-7 receptor (MAS1) were measured by quantitative real-time RT-PCR. Decidual explants were cultured in duplicate for 24 and 48 h, and all RAS mRNA, and the secretion of prorenin, angiotensin II, and angiotensin 1-7 was measured using quantitative real-time RT-PCR, ELISA, and radioimmunoassay, respectively. In the decidua collected before labor, REN mRNA levels were higher if the fetus was female. In addition, REN, ATP6AP2, AGT, and MAS1 mRNA abundance was greater in decidual explants collected from women carrying a female fetus, as was prorenin protein. After 24 h, ACE1 mRNA was higher in the decidual explants from women with a male fetus, whereas after 48 h, both ACE1 and ACE2 mRNA was higher in decidual explants from women with a female fetus. Angiotensin II was present in all explants, but angiotensin 1-7 levels often registered below the lower limits of sensitivity for the assay. After labor, decidua, when compared with nonlaboring decidua, demonstrated lower REN expression when the fetus was female. Therefore, the maternal decidual RAS is regulated in a sex-specific manner, suggesting that it may function differently when the fetus is male than when it is female.

Prenatal programming of the innate immune response following in utero exposure to inflammation: a sexually dimorphic process?

Maternal infection and inflammation are common events during pregnancy. This article documents evidence that suggests such inflammation compromises the development of the fetal innate immune response, in support of an in utero origins hypothesis of neonatal and childhood inflammatory disease. The potential for this response to exhibit sex specificity is also explored, based on evidence of sexually dimorphic placental responses to maternal inflammation.

Prenatal stress, gestational age and secondary sex ratio: the sex-specific effects of exposure to a natural disaster in early pregnancy

BACKGROUND

Previous research suggests that maternal exposure to acute stress has a negative impact on the duration of pregnancy, and that this effect may vary by the time of exposure. It has also been proposed that stress exposure reduces the ratio of male-to-female births. To date, no study has jointly examined both outcomes, although they may be strongly related. Using population-level data with no selectivity, we jointly study the sex-specific effect of stress on the duration of pregnancy and the observed sex ratio among pregnant women exposed to a major earthquake in Chile.

METHODS

In a quasi-experimental design, women exposed to the earthquake in different months of gestation were compared with women pregnant 1 year earlier. Estimates from a comparison group of pregnant women living in areas not affected by the earthquake were also examined to rule out confounding trends. Regression models were used to measure the impact of earthquake exposure on gestational age and preterm birth by sex across month of gestation. A counterfactual simulation was implemented to assess the effect of the earthquake on the secondary sex ratio accounting for the differential impact of stress on gestational age by sex.

RESULTS

Earthquake exposure in Months 2 and 3 of gestation resulted in a significant decline in gestational age and increase in preterm delivery. Effects varied by sex, and were much larger for female than male pregnancies. Among females, the probability of preterm birth increased by 0.038 [95% confidence interval (CI): 0.005, 0.072] in Month 2 and by 0.039 (95% CI: 0.002, 0.075) in Month 3. Comparable increases for males were insignificant at the conventional P < 0.05 level. After accounting for the sex-specific impact on gestational age, a decline in the male-to-female ratio in Month 3 of exposure was detected [-0.058 (95% CI: -0.113, -0.003)].

CONCLUSIONS

Maternal exposure to an exogenous stressor early but not late in the pregnancy affects gestational age and the probability of preterm birth. This effect is much stronger in females than males. Stress exposure in early pregnancy may also contribute to a decline in the ratio of male-to-female live births in exposed cohorts.

Preterm birth seasonality in Greece: an epidemiological study

OBJECTIVE

Seasonality of preterm birth has been noted, although not conclusively studied. Weather is also thought to play a role. We sought preterm birth seasonality and additionally studied the effect of weather parameters in the preterm birth pattern.

METHODS

Vital statistics from the Hellenic Statistical Authority were retrieved, covering the years from 1980 to 2008. Additionally, weather data were retrieved for the years of the study. Time series analysis was used to create various statistical models that would be compared to each other for their accuracy to predict preterm birth. Factors used in the modeling included month of birth, gender and weather factors.

RESULTS

Preterm birth seasonality was exhibited. Two peaks of higher risk of preterm birth were noted: One during summer and one during winter. Males were more influenced by seasonality and exhibited slightly different seasonal patterns than females, although no higher risk for preterm birth was noted. The best model that described seasonal pattern of preterm birth was the one that included meteorological factors. Notably, extreme (hotter or colder) weather was accompanied by an increase in preterm birth.

CONCLUSIONS

Evidence for seasonality of preterm birth was shown and extreme weather was associated with a higher incidence of it.

Sexually dimorphic gene expression in non-human primate ESCs analyzed stringently

Human exhibit sexual dimorphism early in development and throughout life. Here we stringently analyzed gene expression in inbred non-human primate embryonic stem cells (nhpESCs) searching for sexually dimorphisms. We utilized location-specific probes solely, thus avoiding probe cross-reactivity between members of gene families and genomic gene duplications. Seventeen sexually dimorphic transcripts (15 genes, out of which 9 autosomals) were identified, of which five were verified using real-time q-PCR. We compared these results from pedigreed nhpESCs with available human ESCs datasets. Three human X-linked genes show sexual dimorphism. Thus, these results enhance our knowledge and deepen our understanding on early development processes for sexual dimorphism.

The impact of fetal gender on preterm birth in a southern Chinese population

OBJECTIVE

This study was conducted to determine whether carrying a singleton male fetus increases the risk of preterm birth (PTB) in Chinese women.

METHODS

A retrospective cohort study was conducted on women with singleton pregnancies and delivered in our hospital. Maternal characteristics, pregnancy outcome, and incidence of PTB, were compared between women carrying a male versus a female fetus. The independent effect of a male fetus on PTB was examined with multiple logistic regression analysis adjusting for the other confounding factors identified.

RESULTS

There were significant differences in maternal and infant characteristics between women with a male versus a female fetus. Despite similar or lower incidences of complications and labor induction, women with a male fetus had increased birth <37 weeks (7.0% versus 6.2%, p<?0.001) and birth at 34?36 weeks (5.15% versus 4.4%, p<0.001), but not for birth <34 weeks (2.0% versus 1.8%, p=?0.163). Regression analysis confirmed the association between male fetus with birth at 34-36 weeks (aOR 1.11, 95% CI 1.10?1.33) and spontaneous preterm labor (aOR 1.09, 95% CI 1.00-1.19).

CONCLUSIONS

The results confirmed that carrying a male fetus is an independent risk factor for spontaneous preterm labor and PTB at 34?36 weeks gestation in southern Chinese women.