Offspring sex and pregnancy outcome by length of gestation

Reproductive mode and the shifting arenas of evolutionary conflict

In sexually reproducing organisms, the genetic interests of individuals are not perfectly aligned. Conflicts among family members are prevalent since interactions involve the transfer of limited resources between interdependent players. Intrafamilial conflict has traditionally been considered along three major axes: between the sexes, between parents and offspring, and between siblings. In these interactions, conflict is expected over traits in which the resulting phenotypic value is determined by multiple family members who have only partially overlapping fitness optima. We focus on four major categories of animal reproductive mode (broadcast spawning, egg laying, live bearing, and live bearing with matrotrophy) and identify the shared phenotypes or traits over which conflict is expected, and then review the empirical literature for evidence of their occurrence. Major transitions among reproductive mode, such as a shift from external to internal fertilization, an increase in egg-retention time, modifications of embryos and mothers for nutrient transfer, the evolution of postnatal parental care, and increased interaction with the kin network, mark key shifts that both change and expand the arenas in which conflict is played out.

Fetal sex dependency of maternal vascular adaptation to pregnancy: a prospective population-based cohort study

OBJECTIVE

To investigate fetal sex dependency of maternal vascular adaptation to pregnancy as assessed by uteroplacental vascular resistance and maternal blood pressure.

DESIGN

Prospective population-based cohort study.

SETTING

Rotterdam, the Netherlands.

POPULATION

In total, 8224 liveborn singleton pregnancies were included.

METHODS

Maternal vascular adaptation was assessed in all trimesters of pregnancy. Pregnancies were stratified into being either complicated by the placental syndrome (i.e. pre-eclampsia, fetal growth restriction or preterm birth, n = 1229) or uncomplicated (n = 6995).

MAIN OUTCOME MEASURES

First trimester: blood pressures. Second trimester: blood pressures, pulsatility index of the uterine artery (PI-UtA). Third trimester: blood pressures, PI-UtA, presence of notching in the uterine artery.

RESULTS

In women carrying a male fetus PI-UtA was higher than in women with a female fetus in the total group (second trimester P < 0.001, third trimester P = 0.005). Effect estimates differed between women with or without the placental syndrome. In the total group, women with a male fetus more often showed notching in the Doppler resistance pattern (odds ratio 1.42, 95% confidence interval 1.17-1.72). Different blood pressure patterns were observed between pregnant women with a male fetus and pregnant women with a female fetus and between complicated pregnancies and uncomplicated pregnancies.

CONCLUSION

Fetal sex is significantly associated with maternal vascular adaptation to pregnancy with differential effects in uncomplicated pregnancies and in pregnancies complicated by the placental syndrome.

TWEETABLE ABSTRACT

Fetal sex is significantly associated with maternal vascular adaptation to pregnancy.

Preeclampsia and breast cancer: The influence of birth characteristics

BACKGROUND

In parous women preeclampsia has been associated with reduced risk of developing breast cancer. Characteristics of births following preeclamptic pregnancies may help understand mechanisms involved in the breast cancer risk reduction inferred by preeclampsia.

METHODS

We conducted a register-based cohort study of all Danish women giving birth during 1978-2010 (n = 778,701). The association between preeclampsia and breast cancer was evaluated overall and according to birth characteristics by means of incidence rate ratios (IRR) estimated in Poisson regression models.

RESULTS

Compared with women with non-preeclamptic pregnancies only, women with one or more preeclamptic pregnancies were 19% significantly less likely to develop breast cancer (IRR = 0.81 [95% CI 0.72-0.93]). We found some indication of greater risk reduction in women with term births, one or more previous births, and in women giving birth to boys. These findings, however, did not reach statistical significance. Finally, risk reduction was slightly greater following milder forms of preeclampsia.

CONCLUSION

Our data is compatible with an approximately 20% reduction in risk of developing breast cancer following preeclampsia. Although we find some variability according to birth characteristics, the risk reduction inferred by preeclampsia seems applicable to most preeclamptic pregnancies.

Sex ratio of congenital abnormalities in the function of maternal age: a population-based study

Maternal age effect is well-known in the origin of numerical chromosomal aberrations and some isolated congenital abnormalities (CAs). The sex ratio (SR), i.e. number of males divided by the number of males and females together, of most CAs deviates from the SR of newborn population (0.51). The objective of this analysis was to evaluate the possible association of maternal age with the SR of isolated CAs in a population-based large dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-1996. First, SR of 24 CA entities/groups was estimated in 21,494 patients with isolated CA. In the next step SR of different maternal age groups was compared to the mean SR of the given CA-groups. The SR of four CA-groups showed some deviation in certain maternal age groups. Cases with anencephaly had female excess in young mothers (<25 years). Cases with skull's CAs particularly craniosynostosis had a male excess in cases born to women over 30 years. Two other CA groups (cleft lip ± palate and valvar pulmonic stenosis within the group of right-sided obstructive defect of heart) had significant deviation in SR of certain maternal age groups from the mean SR, but these deviations were not harmonized with joining age groups and thus were considered as a chance effect due to multiple testing. In conclusion, our study did not suggest that in general SR of isolated CAs might be modified by certain maternal age groups with some exception such as anencephaly and craniosynostosis.

Paternal obesity in a rodent model affects placental gene expression in a sex-specific manner

Fetal growth restriction (FGR) is a major obstetric complication stemming from poor placental development. We have previously demonstrated that paternal obesity in mice is associated with impaired embryo development and significantly reduced fetal and placental weights. We hypothesised that the FGR observed in our rodent model of paternal diet-induced obesity is associated with alterations in metabolic, cell signalling and stress pathways. Male C57BL/6 mice were fed either a normal or high-fat diet for 10 weeks before sperm collection for IVF and subsequent embryo transfer. On embryonic day 14, placentas were collected and RNA extracted from both male and female placentas to assess mRNA expression of 24 target genes using custom RT-qPCR arrays. Peroxisome proliferator-activated receptor alpha (Ppara) and caspase-12 (Casp12) expression were significantly altered in male placentas from obese fathers compared with normal (P<0.05), but not female placentas. PPARA and CASP12 proteins were localised within the placenta to trophoblast giant cells by immunohistochemistry, and relative protein abundance was determined by western blot analysis. DNA was also extracted from the same placentas to determine methylation status. Global DNA methylation was significantly increased in female placentas from obese fathers compared with normal (P<0.05), but not male placentas. In this study, we demonstrate for the first time that paternal obesity is associated with changes in gene expression and methylation status of extraembryonic tissue in a sex-specific manner. These findings reinforce the negative consequences of paternal obesity before conception, and emphasise the need for more lifestyle advice for prospective fathers.

Placenta expresses anti-Müllerian hormone and its receptor: Sex-related difference in fetal membranes

INTRODUCTION

Anti-Müllerian hormone (AMH) is a member of the transforming growth factor-β superfamily, playing a role in sexual differentiation and recruitment. Since a correlation exists between AMH serum levels in cord blood and fetal sex, the present study aimed to identify mRNA and protein expression of AMH and AMHRII in placenta and fetal membranes according to fetal sex.

METHODS

Placenta and fetal membranes samples (n = 40) were collected from women with singleton uncomplicated pregnancies at term. Identification of AMH protein in placenta and fetal membranes was carried out by immunohistochemistry and AMH and AMHRII protein localization by immunofluorescence, while mRNA expression was assessed by quantitative real-time PCR.

RESULT

AMH and AMHRII mRNAs were expressed by placenta and fetal membranes at term, without any significant difference between males and females. Placental immunostaining showed a syncytial localization of AMH without sex-related differences; while fetal membranes immunostaining was significantly more intense in male than in female fetuses (p < 0,01). Immunofluorescence showed an intense co-localization of AMH and AMHRII in placenta and fetal membranes.

DISCUSSION

The present study for the first time demonstrated that human placenta and fetal membranes expresses and co-localizes AMH and AMHRII. Although no sex-related difference was found for the mRNA expression both in placenta and fetal membranes, a most intense staining for AMH in male fetal membranes supports AMH as a gender specific hormone.

Effects of maternal inflammation and exposure to cigarette smoke on birth weight and delivery of preterm babies in a cohort of indigenous Australian women

Sudden infant death syndrome (SIDS), neonatal deaths, and deaths from infection are higher among Indigenous Australians. This study aimed to determine the effects of inflammatory responses and exposure to cigarette smoke, two important factors associated with sudden death in infancy, on preterm birth, and birth weight in a cohort of Indigenous mothers. Indigenous Australian women (n = 131) were recruited as part of a longitudinal study while attending antenatal care clinics during pregnancy; blood samples were collected up to three times in pregnancy. Serum cotinine, indicating exposure to cigarette smoke, was detected in 50.4% of mothers. Compared with non-Indigenous women, the cohort had 10 times the prevalence of antibodies to Helicobacter pylori (33 vs. 3%). Levels of immunoglobulin G, antibodies to H. pylori, and C-reactive protein (CRP) were all inversely correlated with gestational age (P < 0.05). CRP levels were positively associated with maternal body mass index (BMI; ρ = 0.449, P = 0.001). The effects of cigarette smoke (cotinine) and inflammation (CRP) were assessed in relation to risk factors for SIDS: gestational age at delivery and birth weight. Serum cotinine levels were negatively associated with birth weight (ρ = −0.37, P < 0.001), this correlation held true for both male (ρ = −0.39, P = 0.002) and female (ρ = −0.30, P = 0.017) infants. Cotinine was negatively associated with gestational age at delivery (ρ = −0.199, P = 0.023). When assessed by fetal sex, this was significant only for males (ρ = −0.327, P = 0.011). CRP was negatively associated with gestational age at delivery for female infants (ρ = −0.46, P < 0.001). In contrast, maternal BMI was significantly correlated with birth weight. These data highlight the importance of putting programs in place to reduce cigarette smoke exposure in pregnancy and to treat women with chronic infections such as H. pylori to improve pregnancy outcomes and decrease risk factors for sudden death in infancy.

Regulation of the Renin-Angiotensin System Pathways in the Human Decidua

Pregnancy outcome is influenced, in part, by the sex of the fetus. Decidual renin messenger RNA (REN) abundance is greater in women carrying a female fetus than a male fetus. Here, we explore whether the sex of the fetus also influences the regulation of decidual RAS expression with a known stimulator of renal renin and cyclic adenosine monophosphate (cAMP). Cyclic adenosine monophosphate had no affect on decidual REN expression, since REN abundance was still greater in decidual explants from women carrying a female fetus than a male fetus after cAMP treatment. Cyclic adenosine monophosphate decreased prorenin levels in the supernatant if the fetus was female (ie, prorenin levels were no longer sexually dimorphic) and altered the fetal sex-specific differences in other RAS genes seen in vitro. Therefore, fetal sex influences the decidual renin-angiotensin system response to cAMP. This may be related to the presence of fetal cells in the maternal decidua.

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.

Effects of Fetal Sex on Expression of the (Pro)renin Receptor and Genes Influenced by its Interaction With Prorenin in Human Amnion

Males are more likely to be born preterm than females. The causes are unknown, but it is suggested that intrauterine tissues regulate fetal growth and survival in a sex-specific manner. We postulated that prorenin binding to its prorenin/renin receptor receptor (ATP6AP2) would act in a fetal sex-specific manner in human amnion to regulate the expression of promyelocytic zinc finger, a negative regulator of ATP6AP2 expression as well as 2 pathways that might influence the onset of labor, namely transforming growth factor β1 (TGFB1) and prostaglandin endoperoxide synthase 2 (PTGS2). Our findings demonstrate that there are strong interactions between prorenin, ATP6AP2, and TGFB1 and that this system has a greater capacity in female amnion to stimulate profibrotic pathways, thus maintaining the integrity of the fetal membranes. In contrast, glucocorticoids or other factors independent of the prorenin/prorenin receptor pathway may be important regulators of PTGS2 in human pregnancy.

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.

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.

Do daughters really cause divorce? Stress, pregnancy, and family composition

Provocative studies have reported that in the United States, marriages producing firstborn daughters are more likely to divorce than those producing firstborn sons. The findings have been interpreted as contemporary evidence of fathers' son preference. Our study explores the potential role of another set of dynamics that may drive these patterns: namely, selection into live birth. Epidemiological evidence indicates that the characteristic female survival advantage may begin before birth. If stress accompanying unstable marriages has biological effects on fecundity, a female survival advantage could generate an association between stability and the sex composition of offspring. Combining regression and simulation techniques to analyze real-world data, we ask, How much of the observed association between sex of the firstborn child and risk of divorce could plausibly be accounted for by the joint effects of female survival advantage and reduced fecundity associated with unstable marriage? Using data from the National Longitudinal Survey of Youth (NLSY79), we find that relationship conflict predicts the sex of children born after conflict was measured; conflict also predicts subsequent divorce. Conservative specification of parameters linking pregnancy characteristics, selection into live birth, and divorce are sufficient to generate a selection-driven association between offspring sex and divorce, which is consequential in magnitude. Our findings illustrate the value of demographic accounting of processes which occur before birth-a period when many outcomes of central interest in the population sciences begin to take shape.

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.

Mid-trimester maternal ADAM12 levels differ according to fetal gender in pregnancies complicated by preeclampsia

An overrepresentation of adverse pregnancy outcomes has been observed in pregnancies associated with a male fetus. We investigated the association between fetal gender and candidate biomarkers for preeclampsia. Proteins were quantified in samples taken at 20 weeks from women recruited to the SCreening fOr Pregnancy Endpoints (SCOPE) study (preeclampsia n = 150; no preeclampsia n = 450). In contrast to placental growth factor, soluble endoglin, and insulin-like growth factor acid labile subunit, levels of metallopeptidase domain 12 (ADAM12) at 20 weeks were dependent on fetal gender in pregnancies complicated by preeclampsia, for male (n = 73) fetuses the multiples of the median (MoM; interquartile range [IQR] 1.1-1.5) was 1.3, whereas for female fetuses (n = 75) MoM was 1.1 (1.0-1.3); P < .01. Prediction of preeclampsia using ADAM12 levels was improved for pregnancies associated with a male fetus (area under receiver-operator curve [AUC] 0.73 [95% confidence interval [CI] 0.67-0.80]) than that of a female fetus (AUC 0.62 [0.55-0.70]); P = .03. The data presented here fit a contemporary hypothesis that there is a difference between the genders in response to an adverse maternal environment and suggest that an alteration in ADAM12 may reflect an altered placental response in pregnancies subsequently complicated by preeclampsia.

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.

Strategy for standardization of preeclampsia research study design

Preeclampsia remains a major problem worldwide for mothers and babies. Despite intensive study, we have not been able to improve the management or early recognition of preeclampsia. At least part of this is because of failure to standardize the approach to studying this complex syndrome. It is possible that within the syndrome there may be different phenotypes with pathogenic pathways that differ between the subtypes. The capacity to recognize and to exploit different subtypes is of obvious importance for prediction, prevention, and treatment. We present a strategy for research to study preeclampsia, which will allow discrimination of such possible subtypes and also allow comparison and perhaps combinations of findings in different studies by standardized data and biosample collection. To make studies relevant to current clinical practice, the definition of preeclampsia can be that currently used and accepted. However, more importantly, sufficient data should be collected to allow other diagnostic criteria to be used and applied retrospectively. To that end, we present what we consider to be the minimum requirements for a data set in a study of preeclampsia that will facilitate comparisons. We also present a comprehensive or optimal data set for in-depth investigation of pathophysiology. As we approach the definition of phenotypes of preeclampsia by clinical and biochemical criteria, adherence to standardized protocols will hasten our understanding of the causes of preeclampsia and development of targeted treatment strategies.

Fetal sex specific differences in human placentation: a prospective cohort study

INTRODUCTION

Our objective was to assess fetal sex specific differences in first trimester placental biomarkers of both physiological and pathological pregnancies and their interaction with environmental influences. This study is embedded in the Generation R Study, a prospective cohort study.

METHODS

Only live singleton births were included. Linear regression was performed to assess the effect of sex on first trimester placental biomarkers. Interaction analyses were performed to assess interaction of fetal sex with environmental influences. First trimester soluble fms-like tyrosine kinase (s-Flt1), placental growth factor (PLGF), plasminogen activator inhibitor (PAI-2) and homocysteine levels were assessed.

RESULTS

Significant fetal sex specific differences in placental biomarkers were observed. S-Flt1, PAI-2 and PLGF log transformated concentrations were 0.08 ng/mL (95% CI 0.05; 0.11), 0.07 ng/mL (95% CI 0.06; 0.09) and 0.04 pg/mL (95% CI 0.01; 0.06) higher in case of female as compared to male placentas. In pregnancies complicated by pre-eclampsia (PE), preterm birth (PTB) or a newborn being small for gestational age (SGA) no fetal sex specific differences were observed. Interaction analyses suggest that concentrations of s-Flt1, PLGF and PAI-2 decrease in male placentas in the case of hyperhomocysteinemia but remain equal in female placentas.

DISCUSSION

Fetal sex affects early placentation processes with discrepancies regarding pregnancies complicated by PE, PTB or a newborn being SGA. This suggests that other mechanisms causing these complications may dominate the fetal sex effect. The differences concerning homocysteine suggest that fetal sex dependent placental gene-environment interactions exist.

CONCLUSION

Fetal sex specific differences in placental biomarkers exist.

Impact of sex on perinatal mortality and morbidity in twins

OBJECTIVE

Twin studies offer opportunities to investigate mechanisms underlying sex-associated differences in perinatal outcomes. The objective of the study was to investigate sex-related differences in perinatal complications.

STUDY DESIGN

A cohort of 16,045 twin pregnancies - 32,090 twins - was explored for obstetric complications, perinatal and infant mortality, and neonatal morbidities.

RESULTS

Twin pregnancies with a female fetus had an increased risk for preeclampsia, but otherwise there were no pregnancy complications associated with fetal sex. After birth, female-female twins had lower early neonatal and infant mortality, and lower risk for respiratory morbidities than male-male twins at all gestational ages. In unlike-sexed twin pairs, very preterm males had higher respiratory morbidity than females and, females were at higher risk for being growth restricted.

CONCLUSION

Male-male twins have higher respiratory morbidity and neonatal mortality than female-female twins. In unliked-sexed twin pairs, the males seem to be protected by having a female co-twin.

Maternal factors associated with fetal growth and birthweight are independent determinants of placental weight and exhibit differential effects by fetal sex

Introduction

Maternal nutritional and metabolic factors influence the developmental environment of the fetus. Virtually any nutritional factor in the maternal blood has to pass the placental membranes to reach the fetal blood. Placental weight is a commonly used measure to summarize placental growth and function. Placental weight is an independent determinant of fetal growth and birthweight and modifies the associations between maternal metabolic factors and fetal growth. We hypothesized that maternal factors known to be related to fetal growth, newborn size and body composition are determinants of placental weight and that effects of maternal metabolic factors on placental weight differ between the genders.

Methods

The STORK study is a prospective longitudinal study including 1031 healthy pregnant women of Scandinavian heritage with singleton pregnancies. Maternal determinants (parity, body mass index, gestational weight gain and fasting plasma glucose) of placental weight were explored by linear regression models, stratified by fetal sex.

Results

Parity, maternal BMI, gestational weight gain and fasting glucose had positive effects on placental weight. There was a sex specific effect in these associations. Fasting glucose was significantly associated with placental weight in females but not in males.

Conclusion

Maternal factors known to influence fetal growth, birthweight and neonatal body composition are determinants of placental weight. The effect of maternal factors on placental weight is influenced by sex as illustrated in the relation between maternal glucose and placental weight.

Effect of preeclampsia on placental function: influence of sexual dimorphism, microRNA's and mitochondria

In pregnancy fetal growth and development occur in a sexually dimorphic manner. Male and female fetuses respond differently to the intrauterine environment with males disproportionately suffering from perinatal morbidity and mortality. We have demonstrated placental dysfunction and sexually dimorphic responses in pregnancies complicated by severe preeclampsia. Production of cytokines and apoptosis in the male placenta is heightened relative to that of the female placenta. We also find increased expression and stabilization and a sexual dimorphism in expression of the transcription factor HIF-1α, but a defect in binding to the hypoxia response element with corresponding reduced expression of HIF-1α target genes including VEGF and Glut-1. HIF-1α is involved in crosstalk with the redox sensitive transcription factor NFκB in regulation by cytokines, reactive oxygen species and expression of inflammatory genes. We find increased placental expression and DNA binding of NFκB and a sexually dimorphic response suggesting a role for NFκB in placental dysfunction with preeclampsia. Placental mitochondrial complex III activity and complex I and IV expression are reduced and alterations in mitochondrial morphology are found in preeclampsia and are linked to the hypoxamir miR-210. We propose that with severe PE placental HIF-1α is stabilized by excessive ROS, inflammation and relative hypoxia. This increases the expression of miR-210 in the placenta causing repression of mitochondria-associated target genes, potentially leading to mitochondrial and placental dysfunction. This placental dysfunction may lead to a fetal programming effect that results in disease in later life.

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.

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.

Evidence of sexual dimorphism in the placental function with severe preeclampsia

Preeclampsia (PE) affects 5-8% of pregnancies and is responsible for 18% of maternal deaths in the US, and for long-term complications in mother and child. PE is an inflammatory state and may influence placental function in a sex-specific manner. We determined if there is a sexual dimorphism in the placental inflammatory and apoptotic responses in preeclamptic pregnancies. Placentas were collected from normotensive and preeclamptic pregnancies with either male or female fetuses (MPE and FPE respectively) after c-section at term with no labor. Expression patterns of markers of inflammation measured by ELISA, as well as hypoxia, apoptosis and angiogenesis markers measured by Western blotting were determined in the placenta. Consistent with previous studies, an increase in inflammation, hypoxia, and apoptotic cell death was observed in PE compared to normotensive pregnancies. Levels of TNFα, IL-6 and IL-8, and HIF-1α were significantly greater, whereas the angiogenic marker VEGF was significantly reduced in MPE vs. FPE. Sexual dimorphism was also observed in the activation of cell death: the number of TUNEL-positive cells, and the expression pro-apoptotic markers PUMA and Bax being higher in MPE vs. FPE. We also found an increase in the levels of protein and DNA-binding activity of NFκB p65 in MPE vs. FPE. In summary, we show here that in preeclamptic pregnancies the placentas of males were associated with significantly higher expression of inflammatory, hypoxia and apoptotic molecules but reduced expression of a pro-angiogenic marker compared to placentas of female fetuses. We propose that the transcription factor NFκB p65 might, at least partially, be involved in sexual dimorphism during PE.

Length of human pregnancy and contributors to its natural variation

STUDY QUESTION

How variable is the length of human pregnancy, and are early hormonal events related to gestational length?

SUMMARY ANSWER

Among natural conceptions where the date of conception (ovulation) is known, the variation in pregnancy length spanned 37 days, even after excluding women with complications or preterm births.

WHAT IS KNOWN ALREADY

Previous studies of length of gestation have either estimated gestational age by last menstrual period (LMP) or ultrasound (both imperfect measures) or included pregnancies conceived through assisted reproductive technology.

STUDY DESIGN, SIZE, DURATION

The Early Pregnancy Study was a prospective cohort study (1982-85) that followed 130 singleton pregnancies from unassisted conception to birth, with detailed hormonal measurements through the conception cycle; 125 of these pregnancies were included in this analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We calculated the length of gestation beginning at conception (ovulation) in 125 naturally conceived, singleton live births. Ovulation, implantation and corpus luteum (CL) rescue pattern were identified with urinary hormone measurements. We accounted for events that artificially shorten the natural length of gestation (Cesarean delivery or labor induction, i.e. 'censoring') using Kaplan-Meier curves and proportional hazards models. We examined hormonal and other factors in relation to length of gestation. We did not have ultrasound information to compare with our gold standard measure.

MAIN RESULTS AND THE ROLE OF CHANCE

The median time from ovulation to birth was 268 days (38 weeks, 2 days). Even after excluding six preterm births, the gestational length range was 37 days. The coefficient of variation was higher when measured by LMP (4.9%) than by ovulation (3.7%), reflecting the variability of time of ovulation. Conceptions that took longer to implant also took longer from implantation to delivery (P = 0.02). CL rescue pattern (reflecting ovarian response to implantation) was predictive (P = 0.006): pregnancies with a rapid progesterone rise were longer than those with delayed rise (a 12-day difference in the median gestational length). Mothers with longer gestations were older (P = 0.02), had longer pregnancies in other births (P < 0.0001) and were heavier at birth (P = 0.01). We did not see an association between the length of gestation and several factors that have been associated with gestational length in previous studies: body mass index, alcohol intake, parity or offspring sex.

LIMITATIONS, REASONS FOR CAUTION

The sample size was small and some exposures were rare, reducing power to detect weak associations.

WIDER IMPLICATIONS OF THE FINDINGS

Human gestational length varies considerably even when measured exactly (from ovulation). An individual woman's deliveries tend to occur at similar gestational ages. Events in the first 2 weeks after conception are predictive of subsequent pregnancy length, and may suggest pathways underlying the timing of delivery.

STUDY FUNDING/COMPETING INTEREST

This research was supported by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences. None of the authors has any conflict of interest to declare.

Changes in fetal and neonatal mortality during 40 years by offspring sex: a national registry-based study in Norway

Background

There has been a considerable decline in fetal and neonatal mortality in the Western world. The authors hypothesized that this decline has been largest for boys, since boys have a higher risk of fetal and neonatal death.

Methods

The authors used data from the Medical Birth Registry about all births in Norway to study changes during 1967–2005 in mortality for boys and girls from the 23rd week of pregnancy until one month after birth. Absolute and relative yearly changes in fetal and neonatal death rates were estimated separately for boys and girls.

Results

From 1967 to 2005, the average annual reduction in the overall death rate was greater for boys: 0.47 per 1000 boys (95% CI: 0.45, 0.48) and 0.37 per 1000 girls (95% CI: 0.35, 0.39). These estimates were not affected by adjustments made for changes over time in maternal characteristics. The convergence in death rates by sex was strongest for the first week after birth: average annual reduction in the early neonatal death rate was 0.24 per 1000 boys (95% CI: 0.23, 0.25) and 0.17 per 1000 girls (95% CI: 0.16, 0.18). The death rates for boys and girls also converged during pregnancy and from one week to one month after birth. The relative reduction in death rates was quite similar for boys and girls: the overall death rate fell annually by 4.4% (95% CI: 4.3, 4.6%) for boys and by 4.2% (95% CI: 4.0, 4.4%) for girls.

Conclusions

During the period 1967–2005, the absolute reduction in fetal and neonatal death rates was greatest for boys. The relative reduction in mortality was about the same for both sexes, but the absolute reduction was greatest for boys since the mortality for boys began at a higher level. The convergence of death rates was not due to changes in the composition of mothers, suggesting that convergence has been caused by technological progress.

Changes in neuroactive steroid concentrations after preterm delivery in the Guinea pig

BACKGROUND

Preterm birth is a major cause of neurodevelopmental disorders. Allopregnanolone, a key metabolite of progesterone, has neuroprotective and developmental effects in the brain. The objectives of this study were to measure the neuroactive steroid concentrations following preterm delivery in a neonatal guinea pig model and assess the potential for postnatal progesterone replacement therapy to affect neuroactive steroid brain and plasma concentrations in preterm neonates.

METHODS

Preterm (62-63 days) and term (69 days) guinea pig pups were delivered by cesarean section and tissue was collected at 24 hours. Plasma progesterone, cortisol, allopregnanolone, and brain allopregnanolone concentrations were measured by immunoassay. Brain 5α-reductase (5αR) expression was determined by Western blot. Neurodevelopmental maturity of preterm neonates was assessed by immunohistochemistry staining for myelination, glial cells, and neurons.

RESULTS

Brain allopregnanolone concentrations were significantly reduced after birth in both preterm and term neonates. Postnatal progesterone treatment in preterm neonates increased brain and plasma allopregnanolone concentrations. Preterm neonates had reduced myelination, low birth weight, and high mortality compared to term neonates. Brain 5αR expression was also significantly reduced in neonates compared to fetal expression.

CONCLUSIONS

Delivery results in a loss of neuroactive steroid concentrations resulting in a premature reduction in brain allopregnanolone in preterm neonates. Postnatal progesterone therapy reestablished neuroactive steroid levels in preterm brains, a finding that has implications for postnatal growth following preterm birth that occurs at a time of neurodevelopmental immaturity.

Hypomethylation of the LEP gene in placenta and elevated maternal leptin concentration in early onset pre-eclampsia

In pre-eclampsia, placental leptin is up-regulated and leptin is elevated in maternal plasma. To investigate potential epigenetic regulation of the leptin (LEP) gene in normal and complicated pregnancy, DNA methylation was assessed at multiple reported regulatory regions in placentae from control pregnancies (n=111), and those complicated by early onset pre-eclampsia (EOPET; arising <34 weeks; n=19), late onset pre-eclampsia (LOPET; arising ≥34 weeks; n=18) and normotensive intrauterine growth restriction (nIUGR; n=13). The LEP promoter was hypomethylated in EOPET, but not LOPET or nIUGR placentae, particularly at CpG sites downstream of the transcription start site (-10.1%; P<0.0001). Maternal plasma leptin was elevated in EOPET and LOPET (P<0.05), but not nIUGR, compared with controls. EOPET cases showed a trend towards biallelic LEP expression rather than skewed allelic expression observed in control placentae, suggesting that loss of normal monoallelic expression at the LEP locus is associated with hypomethylation, leading to increased overall LEP expression.

Sex specific differences in fetal middle cerebral artery and umbilical venous Doppler

Background

The incidence of several adverse pregnancy outcomes including fetal growth restriction are higher in pregnancies where the fetus is male, leading to suggestions that placental insufficiency is more common in these fetuses. Placental insufficiency associated with fetal growth restriction may be identified by multi-vessel Doppler assessment, but little evidence exists regarding sex specific differences in these Doppler indices or placental function. This study aims to investigate sex specific differences in fetal and placental perfusion and to correlate these changes with intra-partum outcome.

Methods and Findings

This is a prospective cohort study. We measured Doppler indices of 388 term pregnancies immediately prior to the onset of active labour (≤3 cm dilatation). Fetal sex was unknown at the time of the ultrasound assessment. Information from the ultrasound scan was not made available to clinical staff. Case notes and electronic records were reviewed following delivery. We report significantly lower Middle Cerebral artery pulsatility index (1.34 vs. 1.43, p = 0.004), Middle Cerebral artery peak velocity (53.47 cm/s vs. 58.10 cm/s, p = <0.001), and Umbilical venous flow/kg (56 ml/min/kg vs. 61 ml/min/kg, p = 0.02) in male fetuses. These differences however, were not associated with significant differences in intra-partum outcome.

Conclusion

Sex specific differences in feto-placental perfusion indices exist. Whilst the physiological relevance of these is currently unknown, the identification of these differences adds to our knowledge of the physiology of male and female fetuses in utero. A number of disease processes have now been shown to have an association with changes in fetal haemodynamics in-utero, as well as having a sex bias, making further investigation of the sex specific differences present during fetal life important. Whilst the clinical application of these findings is currently limited, the results from this study do provide further insight into the gender specific circulatory differences present in the fetal period.

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.

Sex differences in coeliac disease risk: a Swedish sibling design study

BACKGROUND

For unknown reasons girls are at an increased risk of coeliac disease compared to boys. However, the observed association might be confounded, since maternal coeliac disease is associated with both an increased risk of the disease in first-degree relatives as well as an increased ratio of girls to boys in offspring.

AIMS

We investigate the effect of sex on the risk of coeliac disease before the age of two years using sibling design.

METHODS

We identified all singleton children (n=792,401) born between 1987 and 1993 in Sweden using the Swedish Medical Birth Registry. Coeliac disease cases (2264) were identified using the Swedish National Inpatient Registry. We applied both conventional population-based Cox regression models and sibling designs modelling the association in sex discordant siblings.

RESULTS

We observed a conclusively increased risk of coeliac disease in girls compared to boys, using both sibling design (hazard ratio 1.67, 95% confidence interval 1.44-1.93) and conventional Cox regression analysis (hazard ratio 1.75, 95% confidence interval 1.61-1.91) that could not be explained by perinatal factors previously associated with the disease.

CONCLUSIONS

We confirm that female sex is causally associated with childhood coeliac disease, but the reasons remains unknown.

A decrease in sex ratio at birth nine months after the earthquake in L'Aquila

Introduction. Multiple factors influence the secondary sex ratio (SSR) including stress, which appears to affect mainly the males born. Objective. We evaluate the effects of the earthquake in L'Aquila on the SSR. Materials and Methods. The SSR for the first six months of 2010 was compared to that of the same period of 2008. The chi-square test and Fisher's test were used for the statistical analysis. Results. Nine months after the earthquake, an important reduction in the SSR was recorded: January 2010 versus January 2008 =0.62 versus 0.96. An overall fall in the SSR was also recorded when the first 3 months of 2010 were compared to the first three months of 2008: 0,82 versus 1,11. When the first three months of 2010 were compared with the second three months of 2010, a statistically significant increase of the sex ratio at birth was noted (0,82 versus 1,27).

Hypertensive diseases in pregnancy and breast cancer risk

Background:

Hypertensive diseases in pregnancy may be associated with a reduced risk of breast cancer. Most previous studies are small and have shown conflicting results.

Methods:

In a cohort of 919 712 women who gave their first birth between 1967 and 2008, with linkage of information from two national registries, we assessed whether women with pregnancy hypertensive diseases are at reduced breast cancer risk. We used Cox regression to estimate hazard ratios (HRs) with 95% confidence intervals (CI).

Results:

Compared with women with a normotensive first pregnancy, women with hypertension or preeclampsia in their first pregnancy had a reduced breast cancer risk (HR 0.83, 95% CI 0.77, 0.90). A reduced risk was consistently observed for hypertensive disease in any pregnancy, for recurrent hypertensive disease in pregnancy, and before and after 50 years of age at breast cancer diagnosis. The association was strongest for women with hypertension in pregnancy, who delivered at term/post-term (HR 0.81, 95% CI 0.75, 0.88) or had a child of average birth weight (HR 0.77, 95% CI 0.69, 0.85).

Conclusion:

Women with pregnancy hypertensive diseases are at reduced breast cancer risk. Whether this association can be attributed to pregnancy-specific events or to underlying biological traits remains unclear.

Excess male mortality and age-specific mortality trajectories under different mortality conditions: a lesson from the heat wave of summer 2003

INTRODUCTION

Our objective was to study the impact of an identical additional stress on male and female mortality with a quasi-experimental study design, using natural variations in summer mortality, including the massive heat wave that struck Europe in 2003.

MATERIAL AND METHODS

The summer daily mortality rates of the population aged 65 and over living in 16 European countries were computed by single age from 1998 to 2003. Using the method of Tukey, we established five categories summarizing the summer daily conditions of mortality (exceptionally high values, minor extremely high values, common values, minor extremely low values, and exceptionally low values).

RESULTS

Whatever the mortality conditions during the summer months, the mortality trajectories by age are exponential for both sexes: males die twice more than females at the age of 65 and their level of mortality linearly converges around the age of 97 to that of the females.

DISCUSSION

Being male remains a major risk factor of mortality during heat waves. This issue was missed by previous epidemiological studies because almost all of them focused only on the relative increase in mortality and not on the sex specific mortality rates which implies being able to estimate the population at risk.

Sex differences in fetal habituation

There is some evidence for sex differences in habituation in the human fetus, but it is unknown whether this is due to differences in central processing (habituation) or in more peripheral processes, sensory or motor, involved in the response. This study examined whether the sex of the fetus influenced auditory habituation at 33 weeks of gestation, and whether this was due to differences in habituation or in the sensory or motor components using a set of four experiments. The first experiment found that female fetuses required significantly fewer stimulus presentations to habituate than males. The second experiment revealed no difference in the spontaneous motor behaviour of male and female fetuses. The third experiment examined auditory intensity thresholds for the stimuli used to habituate the fetus. No differences in thresholds were found between males and females, although there was inter-individual variability in thresholds. A final experiment, using stimuli individualized for that particular fetus' auditory intensity threshold, found that female fetuses habituated faster than males. In combination, the studies reveal that habituation in the human fetus is affected by sex and this is due to a difference in central 'information processing' of the stimuli rather than peripheral aspects of the response. It is argued that male and female fetuses present different neurobehavioural developmental trajectories, with females more advanced at 33 weeks than males. This study suggests that research examining prenatal behaviour should consider the factor of fetal sex. This may be particularly pertinent where there is an intention to use the results diagnostically.

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.

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.

Detection of intergenerational genetic effects with application to HLA-B matching as a risk factor for schizophrenia

BACKGROUND AND METHODS

Association studies using unrelated individuals cannot detect intergenerational genetic effects contributing to disease. To detect these effects, we improve the extended maternal-fetal genotype (EMFG) incompatibility test to estimate any combination of maternal effects, offspring effects, and their interactions at polymorphic loci or multiple SNPs, using any size pedigrees. We explore the advantages of using extended pedigrees rather than nuclear families. We apply our methods to schizophrenia pedigrees to investigate whether the previously associated mother-daughter HLA-B matching is a genuine risk or the result of bias.

RESULTS

Simulations demonstrate that using the EMFG test with extended pedigrees increases power and precision, while partitioning extended pedigrees into nuclear families can underestimate intergenerational effects. Application to actual data demonstrates that mother-daughter HLA-B matching remains a schizophrenia risk factor. Furthermore, ascertainment and mate selection biases cannot by themselves explain the observed HLA-B matching and schizophrenia association.

CONCLUSIONS

Our results demonstrate the power of the EMFG test to examine intergenerational genetic effects, highlight the importance of pedigree rather than case/control or case-mother/control-mother designs, illustrate that pedigrees provide a means to examine alternative, non-causal mechanisms, and they strongly support the hypothesis that HLA-B matching is causally involved in the etiology of schizophrenia in females.

Fetal sex and differential survival in preeclampsia and eclampsia

PURPOSE

We investigate sex differences in the incidence of stillbirth, neonatal mortality, and perinatal mortality among singletons born to mothers with preeclampsia or eclampsia.

METHODS

Retrospective cohort analysis of a population-based sample of singleton births covering the period 1989 through 2005 (n = 56,313).

RESULTS

The study population comprised 26,931 female (47.8%) and 29,382 male infants (52.2%; referent group). Overall, the prevalence of stillbirth, neonatal mortality and perinatal mortality were 0.68, 0.52 and 1.2%, respectively. There was no sex difference in the incidence of stillbirth, neonatal or perinatal mortality among offspring of mothers in this study.

CONCLUSION

Although there was a preponderance of male infants among mothers with preeclampsia or eclampsia, we did not observe any sex-associated differences in fetal or neonatal survival among offspring of mothers with preeclampsia or eclampsia.