Does sex matter? Association of fetal sex and parental age with pregnancy outcomes in Taiwan: a cohort study

Assisted Reproductive Technology, Multiple Births, and Perinatal Outcomes in Taiwan from 2001 to 2020

OBJECTIVE

To investigate the effect of the Assisted Reproduction Act, implemented in 2007 in Taiwan to reduce the number of embryos to transfer, on the trends over time regarding the rate of multiple births, preterm delivery, low birth weight (LBW), and small for gestational age (SGA) among deliveries using assisted reproductive technology (ART).

STUDY DESIGN

From the Birth Reporting Registry and the Assisted Reproduction Registry, we retrieved data of 4 016 530 live birth deliveries between 2001 and 2020; among them 71 000 (1.77%) were after ART. We calculated the rate of multiples and perinatal outcomes per 1000 deliveries annually from 2001 to 2020 for deliveries using and not using ART and computed the population attributable risk. We performed interrupted time series to assess the effect of the intervention, ie, the Assisted Reproduction Act.

RESULTS

The proportion of deliveries following ART was 0.57% in 2001 and increased to 4.03% in 2020. After the intervention, there were decreasing trends over time for rates of multiples (-10.63 per year, P < .001), preterm delivery (-6.74, P = .003), LBW (-9.38, P < .001), and SGA (-4.48, P = .001) among ART deliveries. There was also an immediate decrease right after intervention (-53.45, P = .005) for SGA after ART. The population attributable risk trends before and after intervention were both increasing for all outcomes.

CONCLUSIONS

The Assisted Reproduction Act in Taiwan was associated with a decreasing trend of multiples, preterm delivery, LBW, and SGA over time since 2008 among ART deliveries. In particular, there was an immediate decrease of SGA right after the intervention.

Sexually dimorphic DNA methylation and gene expression patterns in human first trimester placenta

BACKGROUND

Fetal sex and placental development impact pregnancy outcomes and fetal-maternal health, but the critical timepoint of placenta establishment in first trimester is understudied in human pregnancies.

METHODS

Pregnant subjects were recruited in late first trimester (weeks 10-14) at time of chorionic villus sampling, a prenatal diagnostic test. Leftover placenta tissue was collected and stored until birth outcomes were known, then DNA and RNA were isolated from singleton, normal karyotype pregnancies resulting in live births. DNA methylation was measured with the Illumina Infinium MethylationEPIC BeadChip array (n = 56). Differential methylation analysis compared 25 females versus 31 males using a generalized linear model on 743,461 autosomal probes. Gene expression sex differences were analyzed with RNA-sequencing (n = 74). An integrated analysis was performed using linear regression to correlate gene expression and DNA methylation in 51 overlapping placentas.

RESULTS

Methylation analysis identified 151 differentially methylated probes (DMPs) significant at false discovery rate < 0.05, including 89 (59%) hypermethylated in females. Probe cg17612569 (GABPA, ATP5J) was the most significant CpG site, hypermethylated in males. There were 11 differentially methylated regions affected by fetal sex, with transcription factors ZNF300 and ZNF311 most significantly hypermethylated in males and females, respectively. RNA-sequencing identified 152 genes significantly sexually dimorphic at false discovery rate < 0.05. The 151 DMPs were associated with 18 genes with gene downregulation (P < 0.05) in the direction of hypermethylation, including 2 genes significant at false discovery rate < 0.05 (ZNF300 and CUB and Sushi multiple domains 1, CSMD1). Both genes, as well as Family With Sequence Similarity 228 Member A (FAM228A), showed significant correlation between DNA methylation and sexually dimorphic gene expression, though FAM228A DNA methylation was less sexually dimorphic. Comparison with other sex differences studies found that cg17612569 is male-hypermethylated across gestation in placenta and in human blood up to adulthood.

CONCLUSIONS

Overall, sex dimorphic differential methylation with associated differential gene expression in the first trimester placenta is small, but there remain significant genes that may be regulated through methylation leading to differences in the first trimester placenta.

Paternal age and first trimester placental size and growth: The Rotterdam Periconceptional Cohort

INTRODUCTION

Despite a noticeable trend of delayed fatherhood, less is known about the impact of paternal age on the paternally programmed placenta. We hypothesize that paternal aging affects seminal quality and as such induces ageing-related epigenetic alterations that influence placental growth. Our main aim is to investigate associations between paternal age and first trimester (vascular) placental growth trajectories.

METHODS

Pregnant women were enrolled before 10 weeks of gestation in the Rotterdam Periconceptional Cohort (Predict study). Placental volumes (PV) and utero-placental vascular volumes (uPVV) were measured at 7, 9, and 11 weeks gestation. Associations between paternal age and PV and uPVV were investigated using linear mixed models and the maximum likelihood ratio test to test non-linear relationships. We adjusted for gestational age, fetal sex, parental smoking and maternal age, BMI, education and parity, and stratified for conception mode.

RESULTS

From 808 pregnancies we obtained 1313 PV and from 183 pregnancies 345 uPVV measurements. We show no associations between paternal age and PV (p = 0.934) and uPVV (p = 0.489) in our total population or in pregnancies conceived naturally (PV p = 0.166; uPVV p = 0.446) and after IVF/ICSI (PV p = 0.909; uPVV p = 0.749). For example, PV was 0.9% smaller (95% CI -5.7%-7.1%) in fathers aged 40 compared to 30 years old at 9 weeks gestation in the total study population.

DISCUSSION

We are not demonstrating a significant impact of paternal age on first trimester placental growth in a tertiary care population. Given the trend of increasing paternal age, our study should be repeated in the general population.

Paternal age and perinatal outcomes: an observational study

OBJECTIVES

The study's primary aim was to examine the relationship between paternal age and perinatal outcomes.

METHODS

This study used data from two hospital birth registries to examine the association between paternal age and adverse perinatal outcomes. The sample included all live singleton births between 2010 and 2022. The primary exposure was paternal age, and the following perinatal outcomes were considered: mode of conception, mode of delivery, pregnancy complications, and neonatal outcomes.

RESULTS

A total of 15,232 pregnant women were considered. Maternal and paternal ages were 31.9 ± 5.3 and 36.5 ± 6.5 years, respectively. Independent of maternal, paternal age was associated with lower odds of spontaneous conceptions (OR 0.930, 95 % CI 0.968/0.993; p=0.003) and higher odds of intracytoplasmatic sperm injection (OR 1.054, 95 % CI 1.045/1.062; p=0.0001), respectively. In contrast to maternal age, paternal age decreased the odds of any (OR 0.922, 95 % CI 0.985/0.999; p=0.032) and urgent/emergent (OR 0.984, 95 % CI 0.975/0.993; p=0.0001) cesarean delivery. Paternal age did not affect the gestation length, placental or neonatal weight, blood loss during delivery, and neonatal 5th-minute Apgar score.

CONCLUSIONS

Paternal age is associated with perinatal outcomes. These findings suggest that advanced paternal age may have implications for reproductive counseling and prenatal care.

Development and internal validation of a clinical prediction model for spontaneous abortion risk in early pregnancy

OBJECTIVE

This study aimed to develop and internally validate a prediction model for estimating the risk of spontaneous abortion in early pregnancy.

METHODS

This prospective cohort study included 9,895 pregnant women who received prenatal care at a maternal health facility in China from January 2021 to December 2022. Data on demographics, medical history, lifestyle factors, and mental health were collected. A multivariable logistic regression analysis was performed to develop the prediction model with spontaneous abortion as the outcome. The model was internally validated using bootstrapping techniques, and its discrimination and calibration were assessed.

RESULTS

The spontaneous abortion rate was 5.95% (589/9,895) 1. The final prediction model included nine variables: maternal age, history of embryonic arrest, thyroid dysfunction, polycystic ovary syndrome, assisted reproduction, exposure to pollution, recent home renovation, depression score, and stress score 1. The model showed good discrimination with a C-statistic of 0.88 (95% CI 0.87‒0.90) 1, and its calibration was adequate based on the Hosmer-Lemeshow test (p = 0.27).

CONCLUSIONS

The prediction model demonstrated good performance in estimating spontaneous abortion risk in early pregnancy based on demographic, clinical, and psychosocial factors. Further external validation is recommended before clinical application.

Increased stiffness of omental arteries from late pregnant women at advanced maternal age

Advanced maternal age (≥35 years) is a risk factor for poor pregnancy outcomes. Pregnancy requires extensive maternal vascular adaptations, and with age, our blood vessels become stiffer and change in structure (collagen and elastin). However, the effect of advanced maternal age on the structure of human resistance arteries during pregnancy is unknown. As omental resistance arteries contribute to blood pressure regulation, assessing their structure in pregnancy may inform on the causal mechanisms underlying pregnancy complications in women of advanced maternal age. Omental fat biopsies were obtained from younger (<35 years) or advanced maternal age (≥35 years) women during caesarean delivery (n = 7-9/group). Arteries (200-300 µm) were isolated and passive mechanical properties (circumferential stress and strain) assessed with pressure myography. Collagen (Masson's Trichrome) and elastin (Verhoff) were visualized histologically and % positively-stained area was assessed. Median maternal age was 32 years (range 25-34) for younger, and 38 years (range 35-42) for women of advanced maternal age. Circumferential strain was lower in arteries from advanced maternal age versus younger women but circumferential stress was not different. Omental artery collagen levels were similar, while elastin levels were lower with advanced maternal age versus younger pregnancies. The collagen:elastin ratio was greater in arteries from advanced maternal age versus younger women. In conclusion, omental arteries from women of advanced maternal age were less compliant with less elastin compared with arteries of younger controls, which may affect how vascular stressors are tolerated during pregnancy. Understanding how vascular aging affects pregnancy adaptations may contribute to better pregnancy outcomes.

Non-linear Relationship of Maternal Age With Risk of Spontaneous Abortion: A Case-Control Study in the China Birth Cohort

Background

Spontaneous abortion is one of the prevalent adverse reproductive outcomes, which seriously threatens maternal health around the world.

Objective

The current study is aimed to evaluate the association between maternal age and risk for spontaneous abortion among pregnant women in China.

Methods

This was a case-control study based on the China Birth Cohort, we compared 338 cases ending in spontaneous abortion with 1,352 controls resulting in normal live births. The main exposure indicator and outcome indicator were maternal age and spontaneous abortion, respectively. We used both a generalized additive model and a two-piece-wise linear model to determine the association. We further performed stratified analyses to test the robustness of the association between maternal age and spontaneous abortion in different subgroups.

Results

We observed a J-shaped relationship between maternal age and spontaneous abortion risk, after adjusting for multiple covariates. Further, we found that the optimal threshold age was 29.68 years old. The adjusted odds ratio (95% confidence interval) of spontaneous abortion per 1 year increase in maternal age were 0.97 (0.90–1.06) on the left side of the turning point and 1.25 (1.28–1.31) on the right side. Additionally, none of the covariates studied modified the association between maternal age and spontaneous abortion (P > 0.05).

Conclusions

Advanced maternal age (>30 years old) was significantly associated with increased prevalence of spontaneous abortion, supporting a J-shaped association between maternal age and spontaneous abortion.

Placental pathology associated with maternal age and maternal obesity in singleton pregnancy

OBJECTIVE

Maternal age, maternal obesity and neonatal sex dimorphism are known to affect pregnancy and neonatal outcome. However, the effects of these factors on specific placental pathology are less well-documented.

STUDY DESIGN

Clinical information, placental pathology and neonatal data from singleton delivery were collected at our hospital in March 2020 to October 2021 and correlation studies were performed.

RESULTS

A total 3,119 singleton placentas were examined between March 2020 and October 2021 in conjunction with clinical information and neonatal birth data. Advanced maternal age (>35) was significantly associated with a variety of pregnancy complications and placental pathology including preeclampsia/pregnancy induced hypertension (Pre/PIH), gestational diabetes mellitus (GDM2), intrauterine growth restriction (IUGR), and increased maternal body mass index (BMI) at delivery. Maternal obesity (BMI >30 at the time of delivery) was significantly associated with a variety of clinical features and placental pathology including PRE/PIH, GDM2 and decidual vasculopathy (mural arterial hypertrophy). No specific placental pathology was associated with neonatal sex except for more maternal inflammatory response (MIR, chronic deciduitis) in neonates of male sex.

CONCLUSION

Maternal age and maternal obesity were associated with not only clinical complications of pregnancy and neonatal birth weight but also specific placental pathology. Understanding the effects of maternal and environmental factors will help improve pregnancy outcome.

Significance of Sex Differences in ncRNAs Expression and Function in Pregnancy and Related Complications

In the era of personalized medicine, fetal sex-specific research is of utmost importance for comprehending the mechanisms governing pregnancy and pregnancy-related complications. In recent times, noncoding RNAs (ncRNAs) have gained increasing attention as critical players in gene regulation and disease pathogenesis, and as candidate biomarkers in human diseases as well. Different types of ncRNAs, including microRNAs (miRNAs), piwi-interacting RNAs (piRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), participate in every step of pregnancy progression, although studies taking into consideration fetal sex as a central variable are still limited. To date, most of the available data have been obtained investigating sex-specific placental miRNA expression. Several studies revealed that miRNAs regulate the (patho)-physiological processes in a sexually dimorphic manner, ensuring normal fetal development, successful pregnancy, and susceptibility to diseases. Moreover, the observation that ncRNA profiles differ according to cells, tissues, and developmental stages of pregnancy, along with the complex interactions among different types of ncRNAs in regulating gene expression, strongly indicates that more studies are needed to understand the role of sex-specific ncRNA in pregnancy and associated disorders.

The COVID-19 stress may influence on the sex ratio at birth

The ratio of boys to girls (sex ratio) at birth (SRB) is about 1.01-1.05 in most populations and is influenced by various factors, such as maternal stress, maternal inflammation, and endocrine disruption. Male fetus is biologically weaker and more vulnerable to prenatal events than female fetuses. Hence, premature death (and consequently decline the SRB) is higher in boys than girls. The recent coronavirus disease 2019 (COVID-19) has been known to have a variety of stressful and psychological impacts. This stress may consequently enhance maternal inflammation, pregnancy complication, and fetal loss. Also, male fetuses have more adverse outcomes than female fetuses among asymptomatic pregnant women with SARS-Cov-2 infection. Inasmuch as the male fetus are more vulnerable to prenatal events and premature death, it is proposed that the SRB can decline in pregnant women following the COVID-19 stress. However, future studies are needed to define the impact of the COVID-19 on SRB rate.