The human sex ratio from conception to birth

Association of preconception maternal glucocorticoid concentrations with sex ratio at birth: Evidence from a prospective cohort study

PURPOSE

To examine the association between maternal preconception glucocorticoid concentrations and the sex ratio at birth (SRB).

METHODS

We analyzed data from 1,106 pregnant women in a birth cohort study in Lima, Peru, focusing on singleton live births with complete data for preconception glucocorticoids, newborn sex, and covariates. Hair samples of 6 cm were collected in the first trimester and analyzed using LC-MS/MS to extract cortisol (HCC) and cortisone concentrations (HCNC) from the 3-6 cm hair segment. Baseline maternal characteristics were described using descriptive statistics. Unadjusted and adjusted Poisson regressions assessed associations between preconception glucocorticoids and newborn sex.

RESULTS

Most of the samples were Mestizos, multiparous, and married women. The observed SRB was 0.52 (576 males out of 1,106 total births). Adjusted regressions revealed an association between higher preconception HCC and an 8% reduction in male births (95% CI = 0.85, 0.99). Quartile comparisons showed a 13% decline in male births in the highest versus the lowest quartile of preconception HCC, with similar trends seen for HCNC.

CONCLUSION

The observed SRB aligns with global averages, and the inverse relationship between preconception cortisol levels and male births supports prior evidence linking maternal stress to SRB variation. This study underscores the potential role of maternal stress and hypothalamic-pituitary-adrenal axis function in influencing reproductive outcomes.

An observational study of intergenerational sex differences in mortality in Aotearoa New Zealand

Internationally, there are observable sex differentials in mortality in many countries, most notably in affluent countries, with women living longer than men. To understand if this is also the case in Aotearoa New Zealand (NZ), we visualise the precise nature and evolution of sex differentials in mortality by age over time, within a wider context of increasing life expectancy and falling mortality. This allows us to determine if NZ mirrors other affluent countries in having a male/female inequality in mortality, and how the inequality has evolved over several generations in NZ. We use newly available single-year mortality data by sex in NZ to visualise and analyse the sex differentials in mortality using an observational study design. Sex and age-specific mortality data were obtained from the human mortality database from 1948 to 2021 for NZ. The data were then processed to create a smoothed data series using a geometric mean of those two years older and younger as well as aggregating the single-year age groups over 90 into a single category due to small numbers. The processed data was then visualised using a lexis diagram. There are clear patterns of elevated mortality ratios at younger ages (18-30) for males compared to females. The relative difference in mortality inequality between the sexes grew between 1950 and 1980 in NZ, before converging between 2000 and 2020. There is a consistent gap of at least 3 years in life expectancy across the study period by sex. Particularly striking is the longstanding nature of this inequality in mortality by sex in NZ and the relative lack of focus from policymakers. This focus on one country, NZ, allows examination of this specific context to understand how policy changes may have exacerbated or ameliorated trends in male/female mortality inequality.

Prevalence of Congenital Anomalies and Predictive Factors in Pregnant Women in Bahrain: A Retrospective Analysis

Background and Objectives: In Bahrain, congenital anomalies (CAs) account for 8.1% of the total deaths in children under 5, indicating a need to understand the patterns, predictors, and prevalence to improve antenatal standards of care and reduce the burden of disease. This study aimed to determine the prevalence and characteristics of CAs in Bahrain and investigate their association with measured neonatal and maternal risk factors. Method: In this five-year retrospective study, data from 31,615 neonates were analyzed, of which 354 had confirmed CAs. Stillbirths, abortions, and CAs discovered later in life were excluded from the study. Results: The prevalence of CAs was determined to be 1.1% (incidence of 11.2 per 1000 births), with 40.1% of the CAs affecting multiple systems. A statistically significant association was found between CAs and nationality, method of conception, gender, method of delivery, diabetes mellitus status, hypertension, and gestational age at birth. However, the association between CAs and multiple gestations was deemed statistically insignificant. Conclusions: As the first study exploring the associations between CAs and potential risk factors and outcomes in Bahrain, it provided a foundation for further exploration of the topic and insight into factors healthcare providers would target during preconception and antenatal care.

Is 'gender equality in health' the right goal? Exploring issues of definition and measurement

Achieving 'gender equality in health' has been advocated by many as a key goal in health globally; however, we observe this goal has been defined differently by different users. In this paper, we explore the question of how progress towards gender equality in health has been defined and measured, and how the selection of indicators and targets can influence perceptions of who in a population is suffering disadvantage. We summarise the common population health measures-such as life expectancy and risk exposure-and illustrate how each of these measures may lead to different conclusions about gender equality in health. We call for more specificity when defining and measuring gender inequality in health, and propose expanding the focus from 'gender inequalities' (comparison between genders) to also addressing 'within-gender inequities' (a focus that incorporates addressing inequities within different gender identity groups).

Roles of chromosomal and gonadal sex in the fetal and placental responses to maternal food restriction in mice

It is hypothesized that male fetuses are more vulnerable to in utero insults than females due to different growth strategies, and that the placenta contributes to these sex differences. We examined sex differences in the fetal and placental responses to maternal food restriction (∼60% of ad libitum) beginning mid-gestation (Day 11.5). To dissect the roles of chromosomal and gonadal sex, we used the Four Core Genotypes mouse model, which combines deletion of the testis-determining Sry gene from the Y chromosome and autosomal insertion of the Sry gene, such that XX gonadal males and XY gonadal females are produced in addition to XX females and XY males. Food restriction reduced fetal and placental weights but had no effect on the number of viable conceptuses. However, this effect did not differ between gonadal male and female, or between XX and XY, conceptuses. Sex differences in gene expression in both the labyrinth and the combined junctional zone/decidua, as assessed by RNA sequencing, were due entirely to chromosomal sex and not gonadal sex. Food restriction affected the expression of 525 and 665 genes in the labyrinth and the junctional zone/decidua, respectively. However, these effects of food restriction did not differ by gonadal or chromosomal sex when assessed for statistical interactions. In contrast, when analyzing XX and XY placentas separately, hundreds of genes were affected by food restriction in one sex but not in the other, including hundreds of genes not found to be significant in the combined analyses. However, estimated effect sizes were generally similar for XX and XY placentas, suggesting that these sex-stratified analyses greatly exaggerated the extent of sex-dependent responses. Overall, we did not find evidence of the hypothesized sex differences in fetal growth strategy and found that sex differences in placental gene expression were largely due to chromosomal sex.

Trend Analysis of the Sex Ratio at Birth in Greece

INTRODUCTION

The sex ratio at birth, defined as the ratio of male to female live births, is a key indicator in the study of human reproduction and demographic patterns. This study aims to systematically examine the sex ratio in Greece and analyze its temporal trends over the period from 1956 to 2023.

MATERIALS AND METHODS

Data on the total number of live births in Greece, categorized by sex, were obtained from the Hellenic Statistical Authority based on birth certificate records. The sex ratio for each year was calculated as the number of male births per 1,000 female births. Trend analysis was conducted using joinpoint regression and supplemented with linear regression. The annual percent change (APC) and the beta coefficient were computed, along with 95% confidence intervals (95% CIs).

RESULTS

Between 1956 and 2023, a total of 8,215,934 live births were recorded in Greece. The overall sex ratio at birth across all years was 1,068 male births per 1,000 female births, resulting in 269,468 excess male neonates. The gender ratio at birth ranged from a low of 1,047 in 1996 to a high of 1,085 in 2001. In all reported years, the sex ratio at birth was above 1,050, except for 1996. In the most recent year, 2023, the male-to-female ratio at birth was the second lowest of the entire period, at 1,051. Trend analysis revealed that the sex ratio at birth remained stable from 1956 to 1982 (p = 0.862) and showed a statistically significant downward trend from 1982 to 2023, with an annual percent change of -0.0274 (p = 0.004), or an average annual decrease of -0.297 (95% CI: -0.504 to -0.090, p = 0.006) male births per 1,000 female births.

CONCLUSIONS

The sex ratio at birth in Greece has significantly declined over the past four decades, reflecting similar trends observed in other developed nations. Further research is required to investigate the complex biological, demographic, and social factors influencing these trends, providing deeper insight into key aspects of human reproduction.

Prenatal alcohol exposure is associated with altered feto-placental blood flow and sex-specific placental changes

BACKGROUNDPrenatal alcohol exposure (PAE) around conception in preclinical models results in placental insufficiency, likely contributing to offspring abnormalities. Altered placental DNA methylation (DNAm) and gene expression suggest epigenetic mechanisms, perhaps involving impacts on methyl donor levels. PAE around conception in women is common but placental effects are rarely examined. This cohort study investigated associations between PAE around conception and intake/plasma measures of the methyl donors folate and choline, feto-placental blood flow, and placental growth measures, gene expression, and DNAm.METHODSPregnant participants delivered at Mater Mothers' Hospital, Brisbane, Queensland, Australia (n = 411). Dietary intake of choline and folate were calculated and plasma concentrations measured using mass spectrometry (MS) and clinical immunoanalyzer, respectively. Cerebroplacental ratio (CPR) was calculated using Doppler measurements. Placentas were weighed/measured at delivery and samples used to quantify methyl donors (MS), global DNAm (ELISA), and gene expression (quantitative PCR). Data were compared between control/abstinent and PAE groups, by fetal sex.RESULTSA CPR <5th-centile, indicating fetal brain sparing because of placental insufficiency, was found in 2% of controls and 18% of the PAE group, mostly male fetuses (63%). Compared with controls, male PAE placentas had reduced mean thickness and placental growth factor mRNA and DNAm, whereas female PAE placentas had increased S-adenosylmethionine and a trend toward increased DNAm.CONCLUSIONPAE around conception is associated with reduced CPR and altered placental growth measures, particularly in males, with potential implications for future health.FUNDINGNational Health and Medical Research Council (APP1191217) and Mary McConnel Career Boost Program for Women in Paediatric Research (WIS132020).

Prenatal sex determination illuminates the unusual adult sex ratio of a group-living lemur

Most mammals, including humans, exhibit even or slightly male-biased birth sex ratios (BSRs) and female-biased adult sex ratios (ASRs) much later in life due to higher male mortality rates. The group-living primates of Madagascar are unusual in this respect because they lack female-biased ASRs, but it is unknown whether this is the result of skewed BSRs or sex-specific disappearance patterns. Using long-term demographic data from wild red-fronted lemurs (Eulemur rufifrons), we analysed their sex ratio dynamics across the lifespan. We assessed BSR via prenatal sex determination using maternal faecal oestrogen metabolite measurements during late pregnancy, confirming a visually determined equal sex ratio three months after birth, and indicating no early sex-specific mortality. Demographic analyses additionally disclosed higher female disappearance within the first 8 years of age, likely associated with reproductive effort early in life. Thereby, adult male survival had the greatest positive effect on the ASR. Our study offers a rare perspective on the dynamics of age- and sex-specific disappearance in a wild primate population, whose sex-reversed patterns may also contribute to a more general understanding of the mechanisms generating sex-biased mortality.

The influence of fetal sex on maternal blood pressure in pregnancy

Background

Pregnancy with a male fetus carries a higher risk of term pre-eclampsia than pregnancy with a female fetus. Based on evidence that maternal blood pressure (BP) may be raised in pregnancies with Beckwith-Wiedemann syndrome (fetal overgrowth), a possible contributing factor to the association between male sex and term pre-eclampsia is that males grow faster, reaching ~130 g higher birth weight, on average, than females. The association between fetal sex and maternal BP in healthy pregnancies is not known. We hypothesized that male sex would be associated with higher maternal BP in healthy pregnancies, and that this association would be explained by birth weight differences between males and females.

Methods and findings

We tested the association between fetal sex and maternal systolic (SBP) and diastolic blood pressure (DBP), measured at ~28 weeks of gestation, in a meta-analysis of five different cohorts of mother-child pairs (n up to 109,842). Maternal BP was analyzed as both a continuous and dichotomized (high BP: yes or no) outcome. Linear regression models were constructed with and without adjustment for birth weight to assess whether any difference in maternal BP was explained by the difference in birth weight between male and female babies. Lastly, we constructed a fetal genetic score for birth weight using 186 own-birth-weight-associated single-nucleotide polymorphisms (SNPs) to test whether birth-weight-raising-alleles in the fetus were associated with maternal BP in pregnancy (n up to 32,232). Both maternal SBP and DBP were higher in pregnancy when carrying a male fetus compared to a female fetus (mean difference 0.35 mmHg [95%CI: 0.15-0.55] and 0.35 mmHg [95%CI: 0.21-0.49], for SBP and DBP, respectively). An independent effect of fetal sex remained when including birth weight but attenuated slightly (0.22 mmHg [95%CI: 0.02-0.42] and 0.31 mmHg [95%CI: 0.17-0.45], for SBP and DBP respectively). A positive effect estimate was found for odds of experiencing high maternal BP given pregnancy with a male fetus, but confidence intervals were wide (OR 1.05 [95%CI: 0.98-1.12]). No evidence for an association was found between a fetal birth weight genetic score and SBP or DBP when conditioned on maternal genotype.

Conclusions

We found strong evidence to support a small effect of male fetal sex on higher maternal BP in pregnancy and that larger fetal size at birth does not contribute to a substantial part of this association. Our findings do not indicate a difference in maternal BP that would warrant changes to routine monitoring in clinical practice but do suggest that male sex may be a contributing risk factor for BP-related complications.

The Effect of Assisted Reproductive Technologies on Human Sex Ratios

BACKGROUND

Modern assisted reproductive technology (ART), including pre-implantation genetic testing for aneuploidy (PGT-A), has opened new avenues in understanding early embryonic events and has simultaneously raised questions about the impact of ART itself on sex ratios.

AIMS

The primary aim was to investigate whether patient demographic characteristics, ovarian stimulation protocols or laboratory characteristics in ART influence sex ratios. The secondary aim was to relate the blastocyst sex ratio (BSR) to the corresponding secondary sex ratio (SSR) in our patient cohort.

MATERIALS AND METHODS

We conducted a retrospective single-centre cohort study on consecutive PGT-A cycles from January 2019 to February 2022. We analysed demographic data, stimulation protocols, laboratory characteristics and pregnancy outcomes.

RESULTS

The euploidy rate was 45.1% (2608/5777), BSR 1.07 and euploid BSR 1.03. There was no statistical difference in the ploidy status of XX and XY blastocysts and on multivariate logistic regression analysis, there was no association between euploidy and BSR or any other variables examined, including female age and stimulation protocol. The SSR was 1.02 (1294 embryo transfers) with no statistical difference in biochemical pregnancy (p = 0.41), clinical pregnancy (p = 0.56), miscarriage (p = 0.65) or live birth rates (p = 0.40) based on embryo sex.

CONCLUSIONS

Our study indicates that the euploid BSR is not skewed by sex, and there is no relationship between BSR and euploidy, patient characteristics or stimulation protocols. Pregnancy outcomes did not vary by sex, and the SSR was consistent with the SSR of the general Australian population at birth.

Adipose Tissue Macrophages of the Human Fetus

Prenatal adipose tissue development affects body composition and growth trajectory in early infancy, therefore it is a key determinant of adiposity in childhood. Childhood overweight and obesity increase the probability of being obese as an adult. After birth and in adulthood, adipose tissue macrophages (ATMs) are relevant constituents of the fat depots, and they are necessary for physiological adipose tissue development and fat metabolism. In obesity, however, ATMs may induce chronic inflammation leading to insulin resistance, pancreatic beta cell damage and self-immunity. Despite being relevant regulators of adipose tissue development and functioning, it is unknown whether ATMs are present in the fetal adipose tissue, therefore it is elusive whether they may affect the prenatal establishment of fat depots. Here we studied the distribution of ATMs in the human fetus between gestational weeks 17 and 38 and labeled ATMs in the early postnatal life. We found that CD45+/CD14+/CD68+ ATMs infiltrated the fetal adipose tissue from the 17th week of gestation and remained persistent throughout the second and third trimesters. ATMs were phagocytic in the neonate and expressed interleukin-6, along with other pro-inflammatory gene products. These findings show that ATMs colonize the adipose tissue early in gestation, raising the possibility that intrauterine ATM-adipocyte communication may exist, eventually allowing ATMs to affect prenatal adipose tissue development.

Were fewer boys born in the United States during the early months of the COVID-19 pandemic? A test of the Trivers-Willard hypothesis

The Trivers-Willard hypothesis predicts that mammalian parents in poor environmental conditions will favor the offspring sex with more reliable chance of reproductive success, which in humans is females. Three months following the onset of the COVID-19 pandemic in South Africa, England, and Wales, there were significant decreases in the sex ratio at birth (SRB) (male births/total live births). We analyzed this ratio with a seasonal autoregressive moving average model, and a logistic regression, using nationwide natality data for all singleton births in the United States from 2015 to 2021 (n = 25,201,620 total births). We identified no significant change in the sex ratio in either analysis. Rather, we observed marked differences in the sex ratio by maternal characteristics of race/ethnicity, age, and education, with more vulnerable groups having lower sex ratios. These findings suggest the SRB may be an important marker of reproductive vulnerability for disadvantaged groups in the United States.

What about sex, race(ism), and social determinants of health in neonatal outcomes?

Neonatal outcomes encompass a range of outcome measures, including mortality rates, physical and mental health morbidities, and long-term neurodevelopmental statistics. These outcomes are influenced by non-modifiable factors, such as sex and race, and modifiable factors, such as social determinants of health and racism. There is a known bias toward worse outcomes for male infants in terms of preterm birth, low birth weight, and mortality, with several biological and physiological factors contributing to these sex-related differences. In relation to racial disparities, wherein race is a social construct, maternal and infant healthcare continues to lag behind for minority populations compared with the white population, despite advances in medical care. Infants born to Black women have higher infant mortality rates and lower birth weights than infants of white women. These differences can be largely attributed to social and environmental factors, rather than racial and ethnic differences. Furthermore, we emphasize the role of social determinants of health in neonatal outcomes. Factors such as economic stability, education access and quality, healthcare access and quality, the physical neighborhood environment, and the social and community context all contribute to these outcomes. Overall, this article highlights the complex interactions between sex, race(ism), and social determinants of health in neonatal outcomes. It underscores the need for a comprehensive understanding of these factors to improve maternal-neonatal care and reduce disparities in outcomes. Healthcare providers, policymakers, and communities need to work together to combat these complex issues and improve neonatal outcomes for all infants, while understanding the complex interplay between sex, racism, and/or social determinants of health.

The battle of the sexes in humans is highly polygenic

Sex-differential selection (SDS), which occurs when the fitness effects of alleles differ between males and females, can have profound impacts on the maintenance of genetic variation, disease risk, and other key aspects of natural populations. Because the sexes mix their autosomal genomes each generation, quantifying SDS is not possible using conventional population genetic approaches. Here, we introduce a method that exploits subtle sex differences in haplotype frequencies resulting from SDS acting in the current generation. Using data from 300K individuals in the UK Biobank, we estimate the strength of SDS throughout the genome. While only a handful of loci under SDS are individually significant, we uncover highly polygenic signals of genome-wide SDS for both viability and fecundity. Selection coefficients of [Formula: see text] may be typical. Despite its ubiquity, SDS may impose a mortality load of less than 1%. An interesting life-history tradeoff emerges: Alleles that increase viability more strongly in females than males tend to increase fecundity more strongly in males than in females. Finally, we find marginal evidence of SDS on fecundity acting on alleles affecting arm fat-free mass. Taken together, our findings connect the long-standing evidence of SDS acting on human phenotypes with its impact on the genome.

Maternal Folic Acid and Dietary Folate Intake in Relation to Sex Ratio at Birth and Sex-Specific Birth Weight in China

BACKGROUND

It is well-established that prenatal folic acid supplements can reduce neural tube defects. However, the associations between folic acid supplementation, dietary folate intake, and overall folate intake with sex-specific birth outcomes are not yet fully understood.

OBJECTIVES

This study aims to investigate the association of periconceptional folic acid supplement, dietary folate, and total folate intake with the sex ratio at birth and sex-specific birth weight.

METHODS

Data were sourced from a cross-sectional survey conducted between August and December 2013 in Northwest China, involving 7318 infants and their mothers, recruited using a stratified multistage random sampling method. Folic acid supplements (400 μg/d) were ascertained via a retrospective in-person interview. Dietary folate was evaluated using a validated food frequency questionnaire. Birth outcomes, including sex and weight at birth, were obtained from the Medical Certificate of Birth. Generalized linear models were employed to calculate relative risks (RRs) or differences with 95% confidence intervals (CIs).

RESULTS

No association or dose-response relationship was observed between folic acid supplement, dietary folate, and total folate intake during periconception and the likelihood of male births. However, women who took folic acid supplements during pre- and post-conception were associated with an increased male birth weight by 52.8 (8.1 to 97.5) g. Additionally, the total folate intake during periconception was associated with birth weight for males (upper vs. lower tertile: β = 38.8, 95%CI: 5.0 to 72.5 g, p-trend = 0.024) and females (upper vs. lower tertile: β = 42.4, 95%CI: 6.7 to 78.1; p-trend = 0.022).

CONCLUSIONS

Our findings indicate that periconceptional total folate intake does not correlate with sex ratio at birth but was positively linked to infant birth weights, regardless of gender. These findings offer novel insights into potential benefits of total folate intake, beyond the prevention of neural tube defects, for policymakers and public health.

Sex-specific effects of environmental temperature during gestation on fluctuating asymmetry in deciduous teeth

OBJECTIVES

External environmental heat exposure during gestation impacts the physiology of human development in utero, but evidence for these impacts has not yet been explored in dentition. We examined deciduous teeth for fluctuating asymmetry (FA), a measure of developmental instability, together with gestational environmental temperature data drawn from historical weather statistics.

MATERIALS AND METHODS

We measured dental casts from the longitudinal Burlington Growth Study, representing 172 participants (ages 3-6 years) with health records. FA was calculated from crown dimensions and intercuspal distances that develop during gestation. Multiple regression separated by sex (nfemale = 81) examined the effects of mean temperatures in each trimester, controlling for birth year.

RESULTS

In females, increased temperatures during the first trimester are significantly associated with an increase in FA (p = 0.03), specifically during the second and third prenatal months (p = 0.03). There is no relationship between temperature and FA for either sex in the second or third trimesters, when enamel is formed.

DISCUSSION

Dental instability may be sensitive to temperature in the first trimester in females during the scaffolding of crown shape and size in the earliest stages of tooth formation. Sexual dimorphism in growth investment strategies may explain the differences in results between males and females. Using enduring dental characteristics, these results advance our understanding of the effects of temperature on fetal physiology within a discrete period.

Effects of hazardous chemicals on secondary sex ratio: A comprehensive review

The secondary sex ratio (SSR), defined as the ratio of male to female offspring at birth, has garnered significant scientific interest due to its potential impact on population dynamics and evolution. In recent years, there has been a growing concern regarding the potential consequences of environmental chemicals on the SSR, given their widespread exposure and potential enduring ramifications on the reproductive system. While SSR serves as an indicator of health, ongoing research and scientific inquiry are being conducted to explore the potential relationship between chemicals and offspring ratio. Although some studies have suggested a possible correlation, others have yielded inconclusive results, indicating that the topic is intricate and still needs to be elucidated. The precise mechanism by which chemical agents exert their influence on the SSR remains ambiguous, with disruption of the endocrine system being a prominent justification. In light of the complex interplay between chemical exposure and SSR, the present review aims to comprehensively examine and synthesize existing scientific literature to gain a deeper understanding of how specific chemical exposures may impact SSR. Insights into chemical hazards that shift SSR patterns or trends could guide prevention strategies, including legislative bans of certain chemicals, to minimize environmental and public health risks.

Sociodemographic Trends and Perinatal Outcomes in Fathers 50 Years and Older

Importance

The age of fathers at childbirth is rising, with an increasing number of births attributed to older fathers. While the impact of advanced paternal age has been documented, sociodemographic data about fathers aged 50 years and older remain scarce.

Objectives

To explore sociodemographic and temporal trends among the oldest US fathers (age ≥50 years) and their associations with perinatal outcomes.

Design, Setting, and Participants

This retrospective cross-sectional study included data from all US births from 2011 to 2022 using the National Vital Statistics System. Data were analyzed from August 2023 and May 2024.

Exposures

Reported paternal age at childbirth.

Main Outcomes and Measures

Outcomes of interest were sociodemographic factors, temporal trends in older fatherhood, and perinatal outcomes, including preterm birth, low birth weight, gestational diabetes, gestational hypertension, assisted reproductive technology (ART), rates of maternal primiparity, and the infant sex ratio.

Results

From 2011 to 2022, the US recorded 46 195 453 births, with an overall mean (SD) paternal age of 31.5 (6.8) years and 484 507 (1.1%) involving fathers aged 50 years or older, 47 785 (0.1%) aged 60 years or older, and 3777 (0.008%) aged 70 years or older. Births to fathers aged 50 years or older increased from 1.1% in 2011 to 1.3% in 2022 (P for trend < .001). Fathers aged 50 years or older were more diverse, with variations in educational achievement and race and ethnicity. Marital status and maternal racial and ethnic and educational backgrounds also varied by paternal age and race. Despite controlling for maternal age and other sociodemographic and perinatal factors, every 10-year increase in paternal age was consistently associated with greater use of ART (eg, age 50-59 years: adjusted odds ratio [aOR], 2.23; 95% CI, 2.19-2.27), higher likelihood of first maternal birth (eg, age 50-59 years: aOR, 1.16; 95% CI, 1.15-1.17), and increased risks of preterm birth (eg, age 50-59 years: aOR, 1.16; 95% CI, 1.15-1.18) and low birth weight (eg, age 50-59 years: aOR, 1.14; 95% CI, 1.13-1.15) compared with fathers aged 30 to 39 years. No significant changes in the infant sex ratio were observed, except among fathers aged 70 years or older (aOR, 0.92; 95% CI, 0.86-0.99) and 75 years or older (aOR, 0.84; 95% CI, 0.73-0.97), who showed a decreased likelihood of having male offspring.

Conclusions and Relevance

In this cross-sectional study of all US births from 2011 to 2022, the percentage attributed to older fathers, while small, increased. Notable variations in paternal and maternal race and education were identified. Older fatherhood was associated with increased ART use, first-time maternal births, adverse perinatal outcomes, and altered sex ratio. Further research of this population is crucial for improving patient counseling and family planning.

Female-biased birth sex ratio in a female dispersal primate suggests local resource competition

Group living may entail local resource competition (LRC) which can be reduced if the birth sex ratio (BSR) is biased towards members of the dispersing sex who leave the group and no longer compete locally with kin. In primates, the predicted relationship between dispersal and BSR is generally supported although data for female dispersal species are rare and primarily available from captivity. Here, we present BSR data for Phayre's leaf monkeys (Trachypithecus phayrei crepusculus) at the Phu Khieo Wildlife Sanctuary, Thailand (N = 104). In this population, nearly all natal females dispersed, while natal males stayed or formed new groups nearby. The slower reproductive rate in larger groups suggests that food can be a limiting resource. In accordance with LRC, significantly more females than males were born (BSR 0.404 males/all births) thus reducing future competition with kin. This bias was similar in 2-year-olds (no sex-differential mortality). It became stronger in adults, supporting our impression of particularly fierce competition among males. To better evaluate the importance of BSR, more studies should report sex ratios throughout the life span, and more data for female dispersal primates need to be collected, ideally for multiple groups of different sizes and for several years.

Impact of sex, race, and social determinants of health on neonatal outcomes

Despite the global improvements in neonatal outcomes, mortality and morbidity rates among preterm infants are still unacceptably high. Therefore, it is crucial to thoroughly analyze the factors that affect these outcomes, including sex, race, and social determinants of health. By comprehending the influence of these factors, we can work towards reducing their impact and enhancing the quality of neonatal care. This review will summarize the available evidence on sex differences, racial differences, and social determinants of health related to neonates. This review will discuss sex differences in neonatal outcomes in part I and racial differences with social determinants of health in part II. Research has shown that sex differences begin to manifest in the early part of the pregnancy. Hence, we will explore this topic under two main categories: (1) Antenatal and (2) Postnatal sex differences. We will also discuss long-term outcome differences wherever the evidence is available. Multiple factors determine health outcomes during pregnancy and the newborn period. Apart from the genetic, biological, and sex-based differences that influence fetal and neonatal outcomes, racial and social factors influence the health and well-being of developing humans. Race categorizes humans based on shared physical or social qualities into groups generally considered distinct within a given society. Social determinants of health (SDOH) are the non-medical factors that influence health outcomes. These factors can include a person's living conditions, access to healthy food, education, employment status, income level, and social support. Understanding these factors is essential in developing strategies to improve overall health outcomes in communities.

A developmental framework for understanding the influence of sex and gender on health: Pediatric pain as an exemplar

Sex differences are a robust finding in many areas of adult health, including cardiovascular disease, psychiatric disorders, and chronic pain. However, many sex differences are not consistently observed until after the onset of puberty. This has led to the hypothesis that hormones are primary contributors to sex differences in health outcomes, largely ignoring the relative contributions of early developmental influences, emerging psychosocial factors, gender, and the interaction between these variables. In this paper, we argue that a comprehensive understanding of sex and gender contributions to health outcomes should start as early as conception and take an iterative biopsychosocial-developmental perspective that considers intersecting social positions. We present a conceptual framework, informed by a review of the literature in basic, clinical, and social science that captures how critical developmental stages for both sex and gender can affect children's health and longer-term outcomes. The literature on pediatric chronic pain is used as a worked example of how the framework can be applied to understanding different chronic conditions.

Overexpression of Human sFLT1 in the Spongiotrophoblast Is Sufficient to Induce Placental Dysfunction and Fetal Growth Restriction in Transgenic Mice

Preeclampsia (PE) is characterized by maternal hypertension and placental dysfunction, often leading to fetal growth restriction (FGR). It is associated with an overexpression of the anti-angiogenic sFLT1 protein, which originates from the placenta and serves as a clinical biomarker to predict PE. To analyze the impact of sFLT1 on placental function and fetal growth, we generated transgenic mice with placenta-specific human sFLT1 (hsFLT1) overexpression. Immunohistochemical, morphometrical, and molecular analyses of the placentas on 14.5 dpc and 18.5 dpc were performed with a focus on angiogenesis, nutrient transport, and inflammation. Additionally, fetal development upon placental hsFLT1 overexpression was investigated. Dams exhibited a mild increase in serum hsFLT1 levels upon placental hsFLT1 expression and revealed growth restriction of the fetuses in a sex-specific manner. Male FGR fetuses expressed higher amounts of placental hsFLT1 mRNA compared to females. FGR placentas displayed an altered morphology, hallmarked by an increase in the spongiotrophoblast layer and changes in labyrinthine vascularization. Further, FGR placentas showed a significant reduction in placental glycogen storage and nutrient transporter expression. Moreover, signs of hypoxia and inflammation were observed in FGR placentas. The transgenic spongiotrophoblast-specific hsFLT1 mouse line demonstrates that low hsFLT1 serum levels are sufficient to induce significant alterations in fetal and placental development in a sex-specific manner.

Highly cooperative chimeric super-SOX induces naive pluripotency across species

Our understanding of pluripotency remains limited: iPSC generation has only been established for a few model species, pluripotent stem cell lines exhibit inconsistent developmental potential, and germline transmission has only been demonstrated for mice and rats. By swapping structural elements between Sox2 and Sox17, we built a chimeric super-SOX factor, Sox2-17, that enhanced iPSC generation in five tested species: mouse, human, cynomolgus monkey, cow, and pig. A swap of alanine to valine at the interface between Sox2 and Oct4 delivered a gain of function by stabilizing Sox2/Oct4 dimerization on DNA, enabling generation of high-quality OSKM iPSCs capable of supporting the development of healthy all-iPSC mice. Sox2/Oct4 dimerization emerged as the core driver of naive pluripotency with its levels diminished upon priming. Transient overexpression of the SK cocktail (Sox+Klf4) restored the dimerization and boosted the developmental potential of pluripotent stem cells across species, providing a universal method for naive reset in mammals.

Prenatal caffeine exposure induces autism-like behaviors in offspring under a high-fat diet via the gut microbiota-IL-17A-brain axis

Prenatal caffeine exposure (PCE) is a significant contributor to intrauterine growth retardation (IUGR) in offspring, which has been linked to an increased susceptibility to autism spectrum disorder (ASD) later in life. Additionally, a high-fat diet (HFD) has been shown to exacerbate ASD-like behaviors, but the underlying mechanisms remain unclear. In this study, we first noted in the rat model of IUGR induced by PCE that male PCE offspring exhibited typical ASD-like behaviors post-birth, in contrast to their female counterparts. The female PCE offspring demonstrated only reduced abilities in free exploration and spatial memory. Importantly, both male and female PCE offspring displayed ASD-like behaviors when exposed to HFD. We further observed that PCE + HFD offspring exhibited damaged intestinal mucus barriers and disturbed gut microbiota, resulting in an increased abundance of Escherichia coli (E. coli). The induced differentiation of colonic Th17 cells by E. coli led to an increased secretion of IL-17A, which entered the hippocampus through peripheral circulation and caused synaptic damage in hippocampal neurons, ultimately resulting in ASD development. Our strain transplantation experiment suggested that E. coli-mediated increase of IL-17A may be the core mechanism of ASD with a fetal origin. In conclusion, PCE and HFD are potential risk factors for ASD, and E. coli-mediated IL-17A may play a crucial role in fetal-originated ASD through the gut-brain axis.

Variant spectrum of F8 and F9 in hemophilia patients from southern China and 26 novel variants

Hemophilia, an X-linked recessive disorder, is characterized by spontaneous or trauma-induced prolonged bleeding. It is classified as hemophilia A when caused by variants in the F8 gene, and hemophilia B when caused by F9 variants. Few studies have described hemophilia variants in the Chinese population. This study aimed to investigate the clinical and genetic profiles of 193 hemophilia patients from southern China. Utilizing Sanger sequencing, multiplex ligation-dependent probe amplification, gap detection, long-range PCR, and multiplex PCR, we identified both F8 and F9 gene variants. Pregnant women with a history of hemophilia A offspring underwent amniocentesis or villus sampling for the variant detection. Variants in F8 and F9 were pinpointed in 183 patients, with 26 being novel discoveries. Notably, genetic testing was absent in the initial evaluation of 133 out of 161 patients, leading to a protracted average definitive diagnosis timeline of 2 years. Remarkably, two hemophilia A cases with anticipated severe phenotypes due to protein-truncating variants presented with only moderate or mild clinical manifestations. Among the 40 fetuses tested, 34 were males, with 17 exhibiting hemizygous variants in the F8 gene. Our results contribute to the broader understanding of F8 and F9 variant spectrum and highlight the underuse of genetic analyses in southern China.

Seasonal variation in air pollutant levels and its effects on the sex ratio at birth on Fukue island, Japan

BACKGROUND

In general, a slightly higher number of boys are born than girls, and the sex ratio at birth (number of male births/number of female births) is reported to be 1.03-1.07 in many countries. However, pregnant women exposed to high levels of atmospheric particulate matter have a reduced sex ratio at birth. Exposure to air pollutants can also lead to premature birth, suggesting that inflammation within the body may affect pregnancy maintenance and fetal development. On the other hand, the effects of air pollutants carried from afar by monsoons on the sex ratio at birth in downstream areas have not been evaluated. We focused on the Goto Islands, where various air pollutants flow from the Eurasian continent. The objective of this study was to clarify the effects of the atmospheric level of each pollutant on the sex ratio at birth on the Goto Islands.

METHODS

We extracted observation data of particulate matter 2.5, sulfur dioxide, oxidants, nonmethane hydrocarbons, and methane from the National Institute for Environmental Studies database. In addition, the monthly sex ratio at birth was calculated using birth data from the National Statistics Center. To evaluate the effect of substance exposure just before fertilization on the sex ratio at birth, we analyzed the relationship between the observed pollutant level and the sex ratio at birth 9 months later. A stepwise generalized linear model was used to analyze the effects of air pollutant levels on the sex ratio at birth.

RESULTS

The observed values for all pollutants were significantly different between seasons, including the particulate matter 2.5 (p < 0.0001), sulfur dioxide (p = 0.0026), oxidant (p < 0.0001), nonmethane hydrocarbon (p < 0.0001), and methane (p < 0.0001) values. In the target population in the target period, the total number of births was 1835, and the sex ratio at birth was 0.967. Univariate analysis showed that the values of particulate matter 2.5 (p = 0.0157) and oxidants (p = 0.0047) correlated negatively with the sex ratio at birth. In addition, the results of multivariate analysis using the stepwise method in the model equation indicated that every 1 ppm increase in the observed OX value resulted in a 0.311 decrease in the sex ratio at birth (p = 0.0034).

CONCLUSIONS

We evaluated the relationship between seasonal variations in air pollutant levels and the sex ratio at birth 9 months later on the Goto Islands. We found that an increase in oxidant levels just before and after conception may be a risk factor for a lower sex ratio at birth. Due to the previously reported vulnerability of male fetuses, females who become pregnant when air pollutant concentrations are high may be more likely to have a female baby. It is necessary to evaluate the effects of oxidants on various aspects of pregnancy and childbirth.

Fetal growth at term and placental oxidative stress in a tissue micro-array model: a histological and immunohistochemistry study

This study examines 8-hydroxyguanine (8-oxo-Gua) staining in placental tissue samples based on fetal size at birth as well as its relationships with placental histology and other pregnancy variables. This prospective cohort study included women > 18 years with a singleton pregnancy, a live fetus, fluency in Italian, and delivery at term. A total of 165 pregnancies were included in the study. The nuclear syncytiotrophoblast 8-oxo-Gua staining score in LGA was substantially greater than in late FGR (p < 0.05), although the cytoplasm score was lower in SGA and LGA than in AGA (p < 0.05). Furthermore, a sex-specific pattern of 8-oxo-Gua staining was discovered in single-term placentas, with more oxidative damage found in the nuclei of syncytiotrophoblast cells and stromal and endothelial cells in AGA males compared to AGA females (p < 0.05). Second, the histological pattern of late FGR placentae differed by gender. Finally, a significant correlation (p < 0.05) was found between high-intensity 8-oxo-Gua staining in the cytoplasm of syncytiotrophoblast cells and thrombi in the chorionic plate or villi in males. On the other hand, female fetuses demonstrated a significant connection (p < 0.05) between high-intensity 8-oxo-Gua staining in endothelial and stromal cells and high birthweight MoM values. Our findings indicated a significant variation in the oxidative stress pattern between male and female placentae, implying that fetal growth is regulated differently in the two sexes.

Factors affecting male-to-female ratio at birth in frozen-thawed embryo transfer cycles: a large retrospective cohort study

Background

ICSI (intracytoplasmic sperm injection) leads to a reduced male-to-female ratio at birth, whereas blastocyst transfer results in an increased male-to-female ratio. However, limited knowledge exists regarding the impact of these factors on the live birth rate for each gender. This study aimed to investigate the influence of patient characteristics and treatment parameters on the live birth rate for each gender, as well as the ultimate male-to-female ratio at birth in frozen-thawed embryo transfer (FET) cycles.

Method

This retrospective cohort study involved a total of 28,376 FET cycles and 9,217 subsequent deliveries, spanning from January 2003 to December 2015. The study consisted of two parts. First, logistic regression models were constructed to determine the factors influencing the male-to-female ratio among babies born after FET. Second, we aimed to investigate the mechanisms underlying this sex ratio imbalance by analyzing data from all transfer cycles. Generalized estimated equations were employed to assess the impact of risk factors on rates of male and female live births separately.

Results

ICSI resulted in a lower proportion of male offspring compared to in vitro fertilization (IVF) (50.1% vs. 53.7%, aOR: 0.87, 95% CI: 0.80-0.96). Conversely, blastocyst transfer yielded a higher proportion of male offspring than cleavage-stage embryo transfer (58.7% vs. 51.6%, aOR: 1.32, 95% CI: 1.17-1.48). Analysis of all cycles indicated that ICSI resulted in a reduced likelihood of male live birth in comparison to IVF (19.8% vs. 21.6%, aOR: 0.90, 95% CI: 0.83-0.97). However, the transfer of blastocysts rather than cleavage-stage embryos not only increased the chance of male live birth (26.9% vs. 20.2%, aOR: 1.70, 95% CI:1.56-1.85) but also facilitated female live birth (20.3% vs. 19.3%, aOR: 1.26, 95% CI: 1.15-1.39).

Conclusion

ICSI was associated with a reduction in the male-to-female sex ratio and a lower rate of male live births, while blastocyst transfer was associated with an increased male-to-female sex ratio at birth and a higher rate of male live births.

Sex differences in placenta-derived markers and later autistic traits in children

Autism is more prevalent in males and males on average score higher on measures of autistic traits. Placental function is affected significantly by the sex of the fetus. It is unclear if sex differences in placental function are associated with sex differences in the occurrence of autistic traits postnatally. To assess this, concentrations of angiogenesis-related markers, placental growth factor (PlGF) and soluble fms-like tyrosine kinase (sFlt-1) were assessed in maternal plasma of expectant women in the late 1^st (mean= 13.5 [SD = 2.0] weeks gestation) and 2^nd trimesters (mean=20.6 [SD = 1.2] weeks gestation), as part of the Generation R Study, Rotterdam, the Netherlands. Subsequent assessment of autistic traits in the offspring at age 6 was performed with the 18-item version of the Social Responsiveness Scale (SRS). Associations of placental protein concentrations with autistic traits were tested in sex-stratified and cohort-wide regression models. Cases with pregnancy complications or a later autism diagnosis (n = 64) were also assessed for differences in placenta-derived markers. sFlt-1 levels were significantly lower in males in both trimesters but showed no association with autistic traits. PlGF was significantly lower in male pregnancies in the 1^st trimester, and significantly higher in the 2^nd trimester, compared to female pregnancies. Higher PlGF levels in the 2^nd trimester and the rate of PlGF increase were both associated with the occurrence of higher autistic traits (PlGF-2^nd: n = 3469,b = 0.24 [SE = 0.11], p = 0.03) in both unadjusted and adjusted linear regression models that controlled for age, sex, placental weight and maternal characteristics. Mediation analyses showed that higher autistic traits in males compared to females were partly explained by higher PlGF or a faster rate of PlGF increase in the second trimester (PlGF-2^nd: n = 3469, ACME: b = 0.005, [SE = 0.002], p = 0.004). In conclusion, higher PlGF levels in the 2^nd trimester and a higher rate of PlGF increase are associated with both being male, and with a higher number of autistic traits in the general population.

Sex differences in the effects of prematurity and/or low birthweight on neurodevelopmental outcomes: systematic review and meta-analyses

BACKGROUND

Premature birth and/or low birthweight have long-lasting effects on cognition. The purpose of the present systematic review is to examine whether the effects of prematurity and/or low birth weight on neurodevelopmental outcomes differ between males and females.

METHODS

Web of Science, Scopus, and Ovid MEDLINE were searched for studies of humans born premature and/or of low birthweight, where neurodevelopmental phenotypes were measured at 1 year of age or older. Studies must have reported outcomes in such a way that it was possible to assess whether effects were greater in one sex than the other. Risk of bias was assessed using both the Newcastle-Ottawa scale and the National Institutes of Health Quality assessment tool for observational cohort and cross-sectional studies.

RESULTS

Seventy-five studies were included for descriptive synthesis, although only 24 presented data in a way that could be extracted for meta-analyses. Meta-analyses found that severe and moderate prematurity/low birthweight impaired cognitive function, and severe prematurity/low birthweight also increased internalizing problem scores. Moderate, but not severe, prematurity/low birthweight significantly increased externalizing problem scores. In no case did effects of prematurity/low birthweight differ between males and females. Heterogeneity among studies was generally high and significant, although age at assessment was not a significant moderator of effect. Descriptive synthesis did not identify an obvious excess or deficiency of male-biased or female-biased effects for any trait category. Individual study quality was generally good, and we found no evidence of publication bias.

CONCLUSIONS

We found no evidence that the sexes differ in their susceptibility to the effects of severe or moderate prematurity/low birthweight on cognitive function, internalizing traits or externalizing traits. Result heterogeneity tended to be high, but this reflects that one sex is not consistently more affected than the other. Frequently stated generalizations that one sex is more susceptible to prenatal adversity should be re-evaluated.

Chromosomal abnormalities in recurrent pregnancy loss and its association with clinical characteristics

OBJECTIVE

To evaluate the distribution of chromosomal abnormalities in a recurrent pregnancy loss (RPL) cohort and explore the associations between chromosomal abnormalities and clinical characteristics.

METHOD

Over a 5-year period, fresh products of conception (POC) from women with RPL were analyzed by single-nucleotide polymorphism (SNP) array at our hospital. After obtaining the information on clinical characteristics, we investigated the associations between the causative chromosomal abnormalities and clinical characteristics by the chi-squared test or Fisher's exact test and logistic regression.

RESULTS

A total of 2383 cases were enrolled. Overall, 56.9% (1355/2383) were identified with causative chromosomal abnormalities, of which 92.1% (1248/1355) were numerical abnormalities, 7.5% (102/1355) were structural variants, and 0.4% (5/1355) were loss of heterozygosity (LOH). The risk of numerical abnormalities was increased in women with maternal age ≥ 35 years (OR, 1.71; 95% CI, 1.41-2.07), gestational age at pregnancy loss ≤ 12 weeks (OR, 2.78; 95% CI, 1.79-4.33), less number of previous pregnancy losses (twice: OR, 2.32; 95% CI, 1.84-2.94; 3 times: OR, 1.59; 95% CI, 1.23-2.05, respectively), and pregnancy with a female fetus (OR, 1.37; 95% CI, 1.15-1.62). The OR of pregnancy loss with recurrent abnormal CMA was 4.00 (95% CI: 1.87-8.58, P < 0.001) and the adjusted OR was 5.05 (95% CI: 2.00-12.72, P = 0.001). However, the mode of conception was not associated with the incidence of numerical abnormality. No association was noted between structural variants and clinical characteristics.

CONCLUSION

Chromosomal abnormality was the leading cause of RPL. Numerical chromosome abnormality was more likely to occur in cases with advanced maternal age, an earlier gestational age, fewer previous pregnancy losses, and pregnancy with a female fetus.

Sex and gender differences in health and disease. Part I. Evolutionary

Sex affects many aspects of a person's existence, including health. Life expectancy is one of the most telling examples of differences between the sexes. Almost all over the world, women have been found to live longer than men, but the gap in life expectancy varies considerably from country to country. The review discusses the evolutionary mechanisms behind this difference and potential strategies for increasing male life expectancy. Likely processes leading to sex-specific morbidity are also considered.

Pregnancy bias toward boys or girls: The Japan Environment and Children's Study

The sex of the conceived child is a significant concern for parents. To verify whether there women have pregnancy bias toward boys or girls, we investigated whether the history of continuous same-sex pregnancy was associated with the subsequent child's sex. We prospectively analyzed data from the Japan Environment and Children's Study, a birth cohort study. We included all cases of singleton live births (n = 98 412). Women with pregnancy due to infertility treatment were excluded (n = 6255); Similarly, women with a history of miscarriage, artificial abortion, stillbirth, and multiple pregnancies, and those with missing data on the sex of the previous child were excluded. Altogether, 62 718 women were included. For the first live birth, a male-biased sex ratio of 1.055 was observed. Further, no significant difference was found in the sex ratio of the conceived child between women with one boy and those with one girl previously. However, when there were more than two children previously, the subsequently conceived child's male/female sex ratio was significantly higher among boy-only mothers than among girl-only mothers. The results indicated that several pregnant women are biased toward conceiving either boys or girls.

Sex as a Factor in Murine Radiation Research: Implications for Countermeasure Development

There is an increased threat of exposure to ionizing radiation; in the event of such exposure, the availability of medical countermeasures will be vital to ensure the protection of the population. Effective countermeasures should be efficacious across a varied population and most importantly amongst both males and females. Radiation research must be conducted in animal models which act as a surrogate for the human response. Here, we identify differences in survival in male and female C57BL/6 in both a total body irradiation (TBI) model using the Armed Forces Radiobiology Research Institute (AFRRI) 60Co source and a partial body irradiation (PBI) model using the AFRRI Linear Accelerator (LINAC) with 4 MV photons and 2.5% bone marrow shielding. In both models, we observed a higher degree of radioresistance in female animals and a corresponding radiosensitivity in males. One striking difference in male and female rodents is body size/weight and we investigated the role of pre-irradiation body weight on survivability for animals irradiated at the same dose of irradiation (8 Gy TBI, 14 Gy PBI). We found that weight does not influence survival in the TBI model and that heavier males but lighter females have increased survival in the PBI model. This incongruence in survival amongst the sexes should be taken into consideration in the course of developing radiation countermeasures for response to a mass casualty incident.

The Role of Maternal Preconception Adiposity in Human Offspring Sex and Sex Ratio

We evaluated relationships between preconception adiposity and human offspring sex and sex ratio. Using data from a prospective preconception cohort nested within a randomized controlled trial based at 4 US clinical sites (2006-2012), we used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for male:female sex ratio, and log-identity regression to estimate risk differences (RDs) and 95% CIs for male and female livebirth according to preconception adiposity measures. Inverse-probability weights accounted for potential selection bias. Among 603 women attempting pregnancy, there were meaningful reductions in sex ratio for the highest category of each adiposity measure. The lowest sex ratios were observed for obesity (body mass index of ≥30, calculated as weight (kg)/height (m)2, OR = 0.48, 95% CI: 0.26, 0.88) relative to normal body mass index, and the top tertiles (tertile 3) of serum leptin (OR = 0.50, 95% CI: 0.32, 0.80) and skinfold measurements (OR = 0.50, 95% CI: 0.32, 0.79) relative to the lowest tertiles. Reductions were driven by 11-15 fewer male livebirths per 100 women (for obesity, RD = -15, 95% CI: -23, -6.7; for leptin tertile 3, RD = -11, 95% CI: -20, -3.2; and for skinfolds tertile 3, RD = -11, 95% CI: -19, -3.3). We found that relationships between preconception adiposity measures and reduced sex ratio were driven by a reduction in male births.

Sex roles and sex ratios in animals

In species with separate sexes, females and males often differ in their morphology, physiology and behaviour. Such sex-specific traits are functionally linked to variation in reproductive competition, mate choice and parental care, which have all been linked to sex roles. At the 150th anniversary of Darwin's theory on sexual selection, the question of why patterns of sex roles vary within and across species remains a key topic in behavioural and evolutionary ecology. New theoretical, experimental and comparative evidence suggests that variation in the adult sex ratio (ASR) is a key driver of variation in sex roles. Here, we first define and discuss the historical emergence of the sex role concept, including recent criticisms and rebuttals. Second, we review the various sex ratios with a focus on ASR, and explore its theoretical links to sex roles. Third, we explore the causes, and especially the consequences, of biased ASRs, focusing on the results of correlational and experimental studies of the effect of ASR variation on mate choice, sexual conflict, parental care and mating systems, social behaviour, hormone physiology and fitness. We present evidence that animals in diverse societies are sensitive to variation in local ASR, even on short timescales, and propose explanations for conflicting results. We conclude with an overview of open questions in this field integrating demography, life history and behaviour.

Infant sex at birth and long-term maternal mortality

BACKGROUND

Maternal adaptations may vary by foetal sex. Whether male infants influence long-term mortality in mothers remains uncertain.

OBJECTIVE

The objective of the study was to examine whether male infants increase the risk of maternal mortality.

METHODS

This study included pregnant women enrolled at 12 US sites from 1959 to 1966 in the Collaborative Perinatal Project (CPP). Collaborative Perinatal Project records were linked to the National Death Index and the Social Security Master Death File to ascertain deaths until 2016. Foetal sex was determined by infant sex at birth, defined as the total number of male or female infants in pregnancies prior to or during enrolment in the CPP. In secondary analyses, exposure was defined as infant sex at the last CPP delivery. Outcomes included all-cause and underlying causes of mortality. We used Cox proportional hazards models weighted by the number of prior live births and stratified our models by parity and race/ethnicity.

RESULTS

Among 48,188 women, 50.8% had a male infant at their last registered CPP pregnancy and 39.0% had a recorded death after a mean follow-up of 47.8 years (SD 10.5 years). No linear association was found between the number of liveborn males and all-cause mortality (primipara women: HR 1.02, 95% CI 0.95, 1.09, multipara women, 1 prior live birth: HR 0.96, 95% CI 0.89, 1.03, multipara women, ≥2 prior live births: HR 0.97, 95% CI 0.85, 1.11). A similar trend was noted for cardiovascular- and cancer-related mortality. At the last delivery, women with a male infant did not have an increased risk of all-cause or cause-specific mortality compared to women with a female infant. These findings were consistent across racial/ethnic groups.

CONCLUSIONS

Women who give birth to male infants, regardless of number, are not at increased risk of all-cause and cause-specific mortality. These findings suggest that giving birth to male infants may not independently influence the long-term health of women.

Comparative cytogenetics of anembryonic pregnancies and missed abortions in human

Miscarriage is an important problem in human reproduction, affecting 10-15 % of clinically recognized pregnancies. The cases of embryonic death can be divided into missed abortion (MA), for which the ultrasound sign of the embryo death is the absence of cardiac activity, and anembryonic pregnancy (AP) without an embryo in the gestational sac. The aim of this study was to compare the frequency of chromosomal abnormalities in extraembryonic tissues detected by conventional cytogenetic analysis of spontaneous abortions depending on the presence or absence of an embryo. This is a retrospective study of 1551 spontaneous abortions analyzed using GTG-banding from 1990 to 2022 (266 cases of AP and 1285 cases of MA). A comparative analysis of the frequency of chromosomal abnormalities and the distribution of karyotype frequencies depending on the presence of an embryo in the gestational sac was carried out. Statistical analysis was performed using a chi-square test with a p <0.05 significance level. The total frequency of chromosomal abnormalities in the study was 53.6 % (832/1551). The proportion of abnormal karyotypes in the AP and MA groups did not differ significantly and amounted to 57.1 % (152/266) and 52.9 % (680/1285) for AP and MA, respectively (p = 0.209). Sex chromosome aneuploidies and triploidies were significantly less common in the AP group than in the MA group (2.3 % (6/266) vs 6.8 % (88/1285), p = 0.005 and 4.9 % (13/266) vs 8.9 % (114/1285), p = 0.031, respectively). Tetraploidies were registered more frequently in AP compared to MA (12.4 % (33/266) vs. 8.2 % (106/1285), p = 0.031). The sex ratio among abortions with a normal karyotype was 0.54 and 0.74 for AP and MA, respectively. Thus, although the frequencies of some types of chromosomal pathology differ between AP and MA, the total frequency of chromosomal abnormalities in AP is not increased compared to MA, which indicates the need to search for the causes of AP at other levels of the genome organization, including microstructural chromosomal rearrangements, monogenic mutations, imprinting disorders, and epigenetic abnormalities.

Severe cyclones and sex-specific birth outcomes in Queensland, Australia: An interrupted time-series analysis

OBJECTIVES

A male is less adaptable to biological stressors than a female fetus with consequent higher morbidity and mortality. Adverse birth outcomes increase and male livebirths decrease after environmental disasters, economic crises, and terrorist events. We hypothesized the ratio of male to female livebirths would decrease in areas affected by severe tropical cyclones (TCs) in Queensland, Australia. Additionally, in male livebirths, there would be an increase in preterm and low birthweight births. Lastly, we hypothesized that the pregnancy stage at which exposure occurred would modify the association between TC exposure and observed outcomes.

METHODS

Interrupted time series analysis was used to analyze Queensland administrative birth records from July 2007 to June 2018 for significant changes in the sex ratio at birth, measured as the proportion of male livebirths. Adjusted generalized linear models were fitted to births in areas affected by two category five TCs: cyclones Yasi (February 2011) and Marcia (February 2015). To explore male mortality and morbidity risk, additional analysis was conducted on the proportion of male stillborn, low birthweight, and preterm births. The association between estimated pregnancy stage during the TC and the proportion of male births was also analyzed.

RESULTS

Contrary to our hypothesis, increases in the proportion of male livebirths were observed following early-pregnancy exposure to cyclone Yasi and mid-pregnancy exposure to Marcia, although the latter was not statistically significant. No significant changes were observed in proportions of male stillborn, low birthweight, and preterm births.

CONCLUSIONS

This study found a significant association between severe TCs and sex ratio at birth. The stage of pregnancy at which maternal stressors were experienced modified this association. Among people exposed in early to mid-pregnancy, the proportion of male births was higher. This may be because of differential loss of females in utero. Studying sex differences in birth outcomes provides insight into in utero vulnerabilities associated with environmental stressors. Climate change is increasing the intensity and frequency of natural disasters. Understanding fetal vulnerability to environmental stressors will provide crucial information supporting early life health interventions that mitigate the immediate and long-term effects.

Gender bias in fetal malformations: A cross-sectional study in Asian populations

OBJECTIVES

The aim of this study was to detect any gender bias in fetal malformation cases.

DESIGN

This study was a cross-sectional, quantitative survey.

SUBJECTS

Overall, 1,661 Asian fetal malformation cases involving induced abortions in the obstetrics department of the first Affiliated Hospital of Zhengzhou University from 2012 to 2021 were included.

MAIN OUTCOME MEASURES

Measurements of ultrasound detectable structural malformations were classified into 13 subtypes. Karyotyping, single nucleotide polymorphism (SNP) array, or sequencing diagnosis of these fetus was also included in the outcome measures.

RESULTS

The sex ratio (male/female) of all malformation types was 1.446. Cardiopulmonary had the highest proportion of all malformation types with 28%. Diaphragmatic hernia, omphalocele, gastroschisis, nuchal translucency (NT), and Multy malformations had significantly higher proportions of males (p < 0.05). Digestive system malformations had a significantly higher proportion of females (p < 0.05). Maternal age was associated with genetic factors (r = 0.953, p < 0.001) and inversely associated with brain malformations (r = -0.570, p = 0.002). More males were found with trisomy 21, trisomy 18, and monogenetic diseases, while duplications, deletions, and uniparental disomy (UPD) had similar sex ratios between males and females, but not statistically significant.

CONCLUSION

Sex differences are common with fetal malformations, with higher proportions of males. Genetic testing has been proposed to account for these differences.

Epidemiologic and clinical characteristics of selected congenital anomalies at the largest Bosnian pediatric surgery tertiary center

Congenital anomalies (CA) are any abnormality present at birth, either structural or functional, that may potentially affect an infant's health, development, and/or survival. There is a paucity of studies on clinical characteristics and outcomes of CA in Bosnia and Herzegovina, mainly due to the lack of a nationwide congenital malformations monitoring system. A 5-year hospital-based study was conducted to determine the prevalence at birth and clinical characteristics of selected major CA in Sarajevo Canton, Bosnia and Herzegovina. Ninety-one CA were observed from 2012 to 2016 (the overall prevalence was 39.6 cases/10,000 live births). The mean age of neonates at diagnosis was 3 days. The gastrointestinal tract was the most commonly affected system (76.9%), with esophageal atresia (EA) being the most frequent (17.6% of all CA). Major CA were more prevalent among preterm infants than term infants (P = .001), particularly in males (61.5% vs. 38.5%; P = .028; M:F ratio was 1.59). Multiple CA were seen in 37.4% of neonates. The overall mortality rate of neonates was 11%, and the median length of hospital stay was 19.8 days. Our study revealed the distribution and clinical patterns of common major CA in the largest tertiary care facility in Bosnia and Herzegovina. It also confirmed a relatively high mortality rate, which requires further efforts to improve the quality of neonatal care in the country.

Ghosts, Divination, and Magic among the Nuosu: An Ethnographic Examination from Cognitive and Cultural Evolutionary Perspectives

I present a detailed ethnographic study of magic and divination of the Nuosu people in southwest China and offer a cognitive account of the surprising prevalence of these objectively ineffective practices in a society that has ample access to modern technology and mainstream Han culture. I argue that in the belief system of the Nuosu, ghosts, divination, and magical healing rituals form a closely interconnected web that gives sense and meaning to otherwise puzzling practices, and such a belief system is importantly supported and reinforced by individual's everyday experiences. Contemporary Nuosu people overwhelmingly treat these practices as instruments for achieving specific ends and often entertain considerable uncertainty regarding their efficacy, which may be overestimated for a number of reasons, including the following: (1) the intuitive plausibility of divination for ghost identification and exorcist rituals is enhanced by the belief in the existence of ghosts as a result of abductive reasoning, (2) negative instances (divinatory or healing ritual failures) are underreported, and (3) people's misperception of the probability of uncertain events' occurrence often prevents them from realizing that the efficacies of magical/divinatory practices do not outperform chance. I conclude with some comments on the generalizability of the psychological and social mechanisms discussed.

The Male to Female Ratio in Treatment-Warranted Retinopathy of Prematurity: A Systematic Review and Meta-analysis

Importance

Literature and anecdotal evidence suggest a relationship between male sex and retinopathy of prematurity (ROP). It is not known whether a difference, if present, is sex-related pathophysiologic predisposition or sex difference in meeting ROP screening criteria.

Objective

To evaluate the association of sex with the development of treatment-warranted ROP.

Data Sources

PubMed, Embase, and Web of Science databases were searched from 2000 to 2022. The search strategy used keywords including retinopathy of prematurity or ROP or retrolental fibroplasia and treatment or anti-VEGF or bevacizumab or ranibizumab or aflibercept or conbercept or laser or cryotherapy and gender or sex or male or female and medical subject headings terms.

Study Selection

All studies reporting on treatment with anti-vascular endothelial growth factor, laser photocoagulation, and/or cryotherapy for ROP were identified. Studies reporting sex distribution in the treatment group were included in the meta-analysis. Exclusion criteria included case reports, case series of fewer than 10 treated patients, systematic reviews, conference abstracts, letters to the editor, animal studies, and non-English records.

Data Extraction and Synthesis

Two reviewers independently screened and extracted the data following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The proportions of treated male and female infants were combined using random-effects meta-analysis.

Main Outcomes and Measures

Numbers and percentages of male and female infants treated for ROP.

Results

Of 11 368 identified studies, 316 met inclusion criteria, yielding a total of 31 026 treated patients. A higher percentage of male infants were treated for ROP (55% [95% CI, 0.54%-0.55%]), with low heterogeneity between studies (I2 = 34%; P < .001). Thirty-eight studies reported sex distribution in the screened population (170 053 patients; 92 612 [53%] male vs 77 441 [47%] female). There was no significant difference in the odds of receiving treatment between screened male and female infants (pooled odds ratio, 1.04 [95% CI, 0.91-1.18]; P = .67).

Conclusions and Relevance

More male infants are treated for ROP than female infants. This could be due to a known relative pathophysiological fragility of preterm male infants in addition to a difference in ROP screening rates, with more male infants meeting the criteria than female infants. These findings have implications for future studies and may prompt more careful clinical monitoring of male neonates.

Some Aspects of Women’s Health in Republic of Macedonia

INTRODUCTION: Sex and gender "matters" in terms of the health status as well as a result of both biological and gender-related differences. AIM: To analyze sex and gender-based differences in North Macedonia through analysis of some aspects of mortality, the knowledge and attitudes related to women’s health. METHODS: Analysis of the general and age-standardized mortality patterns and CAPI (Computer-assisted personal interview) composed on different topics including women's health for the period 2017-2020 were used. RESULTS: Age-standardized mortality rates (all-causes of death, circulatory and respiratory diseases and neoplasms) are prevalent and higher in the male population in North Macedonia. A significantly higher all-cause mortality trend for both sexes was found in 2020 making this year hardly comparable with the previous years. A decreasing trend of malignant neoplasms rate of female genital organs and an increasing trend of breast cancer mortality is observed. The majority of the respondents (50.6%) rated their current health status as excellent with a statistically significant difference between the age and ethnical groups. One-third of the respondents reported regular physical activity, mostly on a daily basis. The majority (39.3%) are overweight and 27.5% belongs to the obesity class I without a significant difference in terms of ethnicity. Respondents (27%), reported that have high blood pressure, 20.2% vaginal infections, 19.9% allergies, heart issues 15.1%, anemia 11.7%, while diabetes and cancer 8.5% and 2.5% respectively. The youngest and oldest age group of Albanian women are the least informed about the early detection procedures of malignant compared to Macedonian women and other ethnic groups. CONCLUSIONS: Analyzing some aspects of women's health in North Macedonia through the mortality, knowledge and attitudes of Macedonian women, we provide some further evidence for the development and implementation of targeted interventions and policies aimed to reduce the sex and gender-based health inequalities in the country.

Pandemic influenza and gender imbalance: Mortality selection before births

This study uses data from the 1918-1920 influenza pandemic in Japan along with newly digitized and complete census records on births and infant deaths to analyze mortality selection in utero. I find that fetal exposure to the influenza pandemic during the first trimester of the pregnancy decreases the proportion of males at birth. The results from mechanism analysis suggest that this decline in male births is associated with the deterioration of fetal and infant health. This result supports a wide range of existing literature on the long-run adverse effects of pandemic influenza.

First Trimester of Pregnancy as the Sensitive Period for the Association between Prenatal Mosquito Coil Smoke Exposure and Preterm Birth

Mosquito coils are efficient mosquito repellents and mosquito coil smoke (MCS) contributes to indoor air pollution. However, no prior population-based study has investigated whether prenatal MCS exposure is a risk factor for preterm birth (PTB) and whether exposure to MCS in different trimesters of pregnancy is associated with different levels of risk. The sample involved 66,503 mother-child dyads. Logistic regression models were used to examine the relationships between prenatal MCS exposure during different trimesters of pregnancy and PTB. We found that prenatal MCS exposure was associated with a greater likelihood of PTB (OR = 1.12, 95%CI: 1.05-1.20). The prenatal MCS exposure during the first trimester was associated with 1.17 (95%CI: 1.09-1.25) times the odds of being PTB, which was higher than exposure during the second trimester (OR = 1.11, 95%CI: 1.03-1.19) and during the third trimester (OR = 1.08, 95%CI: 1.01-1.16). In the stratified analysis, prenatal MCS exposure significantly increased PTB risk among girls but not among boys. Our results indicated that maternal MCS exposure during pregnancy was associated with PTB and that the first trimester might be the sensitive period. In light of these findings, public health interventions are needed to reduce prenatal exposure to MCS, particularly during the first trimester of pregnancy.

Differential expression of placental 11β-HSD2 induced by high maternal glucocorticoid exposure mediates sex differences in placental and fetal development

A variety of adverse environmental factors during pregnancy cause maternal chronic stress. Caffeine is a common stressor, and its consumption during pregnancy is widespread. Our previous study showed that prenatal caffeine exposure (PCE) increased maternal blood glucocorticoid levels and caused abnormal development of offspring. However, the placental mechanism for fetal development inhibition caused by PCE-induced high maternal glucocorticoid has not been reported. This study investigated the effects of PCE-induced high maternal glucocorticoid level on placental and fetal development by regulating placental 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) expression and its underlying mechanism. First, human placenta and umbilical cord blood samples were collected from women without prenatal use of synthetic glucocorticoids. We found that placental 11β-HSD2 expression was significantly correlated with umbilical cord blood cortisol level and birth weight in male newborns but not in females. Furthermore, we established a rat model of high maternal glucocorticoids induced by PCE (caffeine, 60 mg/kg·d, ig), and found that the expression of 11β-HSD2 in male PCE placenta was decreased and negatively correlated with the maternal/fetal/placental corticosterone levels. Meanwhile, we found abnormal placental structure and nutrient transporter expression. In vitro, BeWo cells were used and confirm that 11β-HSD2 mediated inhibition of placental nutrient transporter expression induced by high levels of glucocorticoid. Finally, combined with the animal and cell experiments, we further confirmed that high maternal glucocorticoid could activate the GR-C/EBPα-Egr1 signaling pathway, leading to decreased expression of 11β-HSD2 in males. However, there was no significant inhibition of placental 11β-HSD2 expression, placental and fetal development in females. In summary, we confirmed that high maternal glucocorticoids could regulate placental 11β-HSD2 expression in a sex-specific manner, leading to differences in placental and fetal development. This study provides the theoretical and experimental basis for analyzing the inhibition of fetoplacental development and its sex difference caused by maternal stress.

Skewed X-Chromosome Inactivation as a Possible Marker of X-Linked CNV in Women with Pregnancy Loss

Skewed X-chromosome inactivation (sXCI) can be a marker of lethal genetic variants on the X chromosome in a woman since sXCI modifies the pathological phenotype. The aim of this study was to search for CNVs in women with miscarriages and sXCI. XCI was assayed using the classical method based on the amplification of highly polymorphic exon 1 of the androgen receptor (AR) gene. The XCI status was analysed in 313 women with pregnancy loss and in 87 spontaneously aborted embryos with 46,XX karyotype, as well as in control groups of 135 women without pregnancy loss and 64 embryos with 46,XX karyotype from induced abortions in women who terminated a normal pregnancy. The frequency of sXCI differed significantly between women with miscarriages and women without pregnancy losses (6.3% and 2.2%, respectively; p = 0.019). To exclude primary causes of sXCI, sequencing of the XIST and XACT genes was performed. The XIST and XACT gene sequencing revealed no known pathogenic variants that could lead to sXCI. Molecular karyotyping was performed using aCGH, followed by verification of X-linked CNVs by RT-PCR and MLPA. Microdeletions at Xp11.23 and Xq24 as well as gains of Xq28 were detected in women with sXCI and pregnancy loss.