Low Gestational Weight Gain Skews Human Sex Ratios towards Females

Impact of diet-induced maternal obesity on the reproductive capacity of F1 female offspring and the early development of the second generation

The aim of this study was to examine the impact of maternal obesity on the reproductive capacity of the female offspring (F1) and on the early development of the second generation (F2). To this end, rats were fed either standard (SD) or cafeteria (CD) diet. CD rats and their offspring were divided into two groups: rats with 18% and ≥25% overweight (CD18 and CD25, respectively) and offspring from CD18 and CD25 rats (OCD18 and OCD25, respectively). Both OCD groups achieved greater weight gain than controls, without changes in the serum levels of glucose, cholesterol or triglycerides. However, they showed increased gonadal cholesterol concentration and fat content compared to controls. Female OCD groups showed a slight prolongation of the estrous cycle and different pattern of changes in the weight gain during pregnancy. The OCD25 group displayed an increased fertility index and pre-implantation losses, and changes in some fetal measurements. Some OCD25 dams gave birth to a larger litter of pups and displayed a lower viability index and lactation rate than controls. OCD25 dams also showed an increase in estradiol and a decrease in testosterone and anti-Müllerian hormone. OCD25 rats showed increased mRNA levels of steroidogenenic enzymes. The offspring from OCD25 females (F2OCD25 offspring) showed early vaginal opening and higher ovulation rate in females, and lower ano-genital distances in males, compared to controls. In conclusion, these results reflect that maternal obesity impacts on the reproductive health of successive generations, probably as a result of epigenetic changes in different systems, including germ cells.

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.

Origin of Sex-Biased Mental Disorders: An Evolutionary Perspective

Sexual dimorphism or sex bias in diseases and mental disorders have two biological causes: sexual selection and sex hormones. We review the role of sexual selection theory and bring together decades of molecular studies on the variation and evolution of sex-biased genes and provide a theoretical basis for the causes of sex bias in disease and health. We present a Sexual Selection-Sex Hormone theory and show that male-driven evolution, including sexual selection, leads to: (1) increased male vulnerability due to negative pleiotropic effects associated with male-driven sexual selection and evolution; (2) increased rates of male-driven mutations and epimutations in response to early fitness gains and at the cost of late fitness; and (3) enhanced female immunity due to antagonistic responses to mutations that are beneficial to males but harmful to females, reducing female vulnerability to diseases and increasing the thresholds for disorders such as autism. Female-driven evolution, such as reproduction-related fluctuation in female sex hormones in association with stress and social condition, has been shown to be associated with increased risk of certain mental disorders such as major depression disorder in women. Bodies have history, cells have memories. An evolutionary framework, such as the Sexual Selection–Sex Hormone theory, provides a historical perspective for understanding how the differences in the sex-biased diseases and mental disorders have evolved over time. It has the potential to direct the development of novel preventive and treatment strategies.

Sex differences in health and disease: A review of biological sex differences relevant to cancer with a spotlight on glioma

The influence of biological sex differences on human health and disease, while being increasingly recognized, has long been underappreciated and underexplored. While humans of all sexes are more alike than different, there is evidence for sex differences in the most basic aspects of human biology and these differences have consequences for the etiology and pathophysiology of many diseases. In a disease like cancer, these consequences manifest in the sex biases in incidence and outcome of many cancer types. The ability to deliver precise, targeted therapies to complex cancer cases is limited by our current understanding of the underlying sex differences. Gaining a better understanding of the implications and interplay of sex differences in diseases like cancer will thus be informative for clinical practice and biological research. Here we review the evidence for a broad array of biological sex differences in humans and discuss how these differences may relate to observed sex differences in various diseases, including many cancers and specifically glioblastoma. We focus on areas of human biology that play vital roles in healthy and disease states, including metabolism, development, hormones, and the immune system, and emphasize that the intersection of sex differences in these areas should not go overlooked. We further propose that mathematical approaches can be useful for exploring the extent to which sex differences affect disease outcomes and accounting for those in the development of therapeutic strategies.

Pre- and post-natal factors and physical activity in childhood: The Norwegian Mother, Father and Child Cohort study

Few studies have examined the possibility that pre- and post-natal factors may be non-linearly associated with later physical activity. We used data from the Norwegian Mother, Father and Child Cohort study (MoBa) and the Medical Birth Registry of Norway (MBRN), including 48 672 children with available data on leisure time physical activity (LTPA) at child's age 7 years. Restricted cubic and linear splines or linear regression was used to examine the associations between maternal pre-pregnancy BMI, birth weight for gestational age, and infant weight gain from birth to 1 year with LTPA (frequency/wk) in 7-year-old children. The results suggest no associations between maternal pre-pregnancy BMI, birth weight, and infant weight gain on subsequent LTPA in girls. Maternal pre-pregnancy BMI and birth weight may be non-linearly associated with LTPA in 7-year-old boys. Infant weight gain (change in weight z-score from birth to 1 year) may be weakly linearly associated with LTPA in boys. Pre- and post-natal factors may therefore influence LTPA in childhood differently in boys and girls. Maternal pre-pregnancy BMI and birth weight are positively associated with LTPA at the lower ends of the maternal pre-pregnancy BMI and birth weight continuums in boys. The negative associations at the higher ends of the continuums and the positive association between infant weight gain and LTPA in boys may not be important and needs further replication.

Mitochondria Inspire a Lifestyle

Tucked inside our cells, we animals (and plants, and fungi) carry mitochondria, minuscule descendants of bacteria that invaded our common ancestor 2 billion years ago. This unplanned breakthrough endowed our ancestors with a convenient, portable source of energy, enabling them to progress towards more ambitious forms of life. Mitochondria still manufacture most of our energy; we have evolved to invest it to grow and produce offspring, and to last long enough to make it all happen. Yet because the continuous generation of energy is inevitably linked to that of toxic free radicals, mitochondria give us life and give us death. Stripping away clutter and minutiae, here we present a big-picture perspective of how mitochondria work, how they are passed on virtually only by mothers, and how they shape the lifestyles of species and individuals. We discuss why restricting food prolongs lifespan, why reproducing shortens it, and why moving about protects us from free radicals despite increasing their production. We show that our immune cells use special mitochondria to keep control over our gut microbes. And we lay out how the fabrication of energy and free radicals sets the internal clocks that command our everyday rhythms-waking, eating, sleeping. Mitochondria run the show.

Maternal Intuition of Fetal Gender

Purpose

Fetal gender speculation is a preoccupation of many expecting parents, and pregnant women commonly profess to intuitively know the gender of their unborn babies. This study objectively compared pregnant mothers' perceptions of fetal gender to sonographically proven gender determinations. Also, success rates from previously published studies, noninvasive prenatal testing and a myriad of gender determination methods were observed and reported for context.

Methods

All pregnant women presenting for second-trimester screening ultrasound (at 17-23 weeks gestation) in the obstetrics department of a single health center were asked to participate. A medical sonographer described the ultrasound examination, obtained appropriate consent and medical history. Each mother was asked if she had any perception as to the fetal gender and her answer documented. Mothers who had foreknowledge of fetal gender were excluded. Frequencies of actual gender were compared with observed frequencies of the maternal prediction using chi-squared test.

Results

Approximately 40% (n=411) of our study population (N=1,026) indicated having an intuition or perception of fetal gender. These women correctly predicted the gender of their babies 51% of the time (P=0.6571). Women who expressed a "strong" degree of intuition (n=53) fared better, accurately predicting fetal gender at a rate of 62%, though the difference in this smaller subcohort also failed to demonstrate statistical significance (P=0.0741).

Conclusions

Intuition of fetal gender is professed by almost half of mothers though, when present, is no better at accurately predicting fetal gender than flipping a coin.

Who is most affected by prenatal alcohol exposure: Boys or girls?

OBJECTIVE

To examine outcomes among boys and girls that are associated with prenatal alcohol exposure.

METHODS

Boys and girls with fetal alcohol spectrum disorders (FASD) and randomly-selected controls were compared on a variety of physical and neurobehavioral traits.

RESULTS

Sex ratios indicated that heavy maternal binge drinking may have significantly diminished viability to birth and survival of boys postpartum more than girls by age seven. Case control comparisons of a variety of physical and neurobehavioral traits at age seven indicate that both sexes were affected similarly for a majority of variables. However, alcohol-exposed girls had significantly more dysmorphology overall than boys and performed significantly worse on non-verbal IQ tests than males. A three-step sequential regression analysis, controlling for multiple covariates, further indicated that dysmorphology among girls was significantly more associated with five maternal drinking variables and three distal maternal risk factors. However, the overall model, which included five associated neurobehavioral measures at step three, was not significant (p=0.09, two-tailed test). A separate sequential logistic regression analysis of predictors of a FASD diagnosis, however, indicated significantly more negative outcomes overall for girls than boys (Nagelkerke R²=0.42 for boys and 0.54 for girls, z=-2.9, p=0.004).

CONCLUSION

Boys and girls had mostly similar outcomes when prenatal alcohol exposure was linked to poor physical and neurocognitive development. Nevertheless, sex ratios implicate lower viability and survival of males by first grade, and girls have more dysmorphology and neurocognitive impairment than boys resulting in a higher probability of a FASD diagnosis.

Twinning in Norway Following the Oslo Massacre: Evidence of a ‘Bruce Effect’ in Humans

Emerging theory and empirical work suggest that the ‘Bruce Effect’, or the increase in spontaneous abortion observed in non-human species when environments become threatening to offspring survival, may also appear in humans. We argue that, if it does, the effect would appear in the odds of twins among male and female live births. We test the hypothesis, implied by our argument, that the odds of a twin among male infants in Norway fell below, while those among females rose above, expected levels among birth cohorts in gestation in July 2011 when a deranged man murdered 77 Norwegians, including many youths. Results support the hypothesis and imply that the Bruce Effect operates in women to autonomically raise the standard of fetal fitness necessary to extend the gestation of twins. This circumstance has implications for using twins to estimate the relative contributions of genes and environment to human responses to exogenous stimuli.

Maternal hypoglycemia on 50 g glucose challenge test: outcomes are influenced by fetal gender

OBJECTIVE

To assess the perinatal outcomes in pregnant women with maternal hypoglycemia following a second trimester oral glucose challenge test (GCT).

MATERIALS AND METHODS

This retrospective case control study consisted of 2091 pregnant women with hypoglycemia (glucose levels >88 mg/dL 1 h following a 50 g GCT in the second trimester of pregnancy) and a control group of 2091 pregnant women with a GCT result between 88 and 130 mg/dL. Perinatal and neonatal characteristics obtained from electronic medical records were compared between groups.

RESULTS

The rates of pregnancy complications were similar in both groups, with the exception of a lower incidence of polyhydramnios and a higher rate of deliveries before the 34th week of gestation in patients with hypoglycemia (0.5% vs. 1.1%, P=0.016 vs. 2.6% vs. 1.7%, P=0.033); respectively. Neonates born to mothers with hypoglycemia had significantly less birth trauma (0.3% vs. 0.9%, P=0.027) and neonatal hypoglycemia. When the data for male and female infants were analyzed separately, male infants had a 1.5-fold (95% CI: 1.05-2.18) increased chance of being small for gestational age (SGA), whereas the risk for female infants did not increase (OR: 0.79, 95% CI: 0.56-1.11).

CONCLUSION

A low maternal plasma glucose level on the GCT is associated with favorable outcomes, such as decreased rates of birth trauma and neonatal hypoglycemia. In addition, male infants have a higher risk of being SGA than female infants when maternal GCT results were <88 mg/dL.

The human sex ratio from conception to birth

We describe the trajectory of the human sex ratio from conception to birth by analyzing data from (i) 3- to 6-d-old embryos, (ii) induced abortions, (iii) chorionic villus sampling, (iv) amniocentesis, and (v) fetal deaths and live births. Our dataset is the most comprehensive and largest ever assembled to estimate the sex ratio at conception and the sex ratio trajectory and is the first, to our knowledge, to include all of these types of data. Our estimate of the sex ratio at conception is 0.5 (proportion male), which contradicts the common claim that the sex ratio at conception is male-biased. The sex ratio among abnormal embryos is male-biased, and the sex ratio among normal embryos is female-biased. These biases are associated with the abnormal/normal state of the sex chromosomes and of chromosomes 15 and 17. The sex ratio may decrease in the first week or so after conception (due to excess male mortality); it then increases for at least 10-15 wk (due to excess female mortality), levels off after ∼20 wk, and declines slowly from 28 to 35 wk (due to excess male mortality). Total female mortality during pregnancy exceeds total male mortality. The unbiased sex ratio at conception, the increase in the sex ratio during the first trimester, and total mortality during pregnancy being greater for females are fundamental insights into early human development.