Association between peri-conceptional bisphenol A exposure in women and men and time to pregnancy-The HOPE study

Assessing preconception exposure to environmental chemicals and fecundity: Strategies, challenges, and research priorities

In 2022, approximately one out of six people globally experienced infertility at some point in their life. Environmental chemicals, particularly those with endocrine disrupting activity, may contribute to impaired fecundity and infertility. We review existing prospective cohort studies of environmental chemicals and fecundity, identify methodological challenges and biases, and outline future research priorities. Studies of preconception environmental chemical exposures and fecundity have occurred in US, Singapore, China and Denmark with recruitment as early as 1982-1986, as recent as 2015-2017 and sample sizes ranging from 99 to 936. Higher exposure to certain chemicals (e.g. heavy metals, perfluoroalkyl substances) was associated with longer time to pregnancy; yet the literature is scarce or nonexistent for many chemicals. Furthermore, prospective studies face challenges and potential biases related to recruiting participants prior to conception, measuring environmental chemicals during critical windows of exposure, and ascertaining when pregnancy occurred. Research priorities include expanding the scope of biomonitoring data collected during the preconception period, continuing to develop and validate analytic methods for self-sampled biospecimens in traditional and novel matrices, collecting data in male partners and investigating etiologic associations according to indicators of marginalization.

The current situation and future directions for the study on time-to-pregnancy: a scoping review

Introduction

As problems associated with infertility and population aging increase, there is a growing interest in the factors that cause a decline in human fertility. Time-to-pregnancy (TTP) is a good indicator with which to reflect human fecundability. Here, we present a comprehensive overview of this topic.

Methods

Relevant qualitative and quantitative studies were identified by searching the Web of science and PubMed electronic databases. We included all literature, written in English, from inception to the 10th April 2021 providing the focus was on TTP. We conducted a narrative synthesis using thematic analysis.

Results

Traditional TTP-related study protocols include prospective and retrospective cohorts that provide a wealth of data to reveal potential influences on TTP. Thus far, a variety of factors have been shown to be associated with TTP in couples preparing for pregnancy, including basic demographic characteristics, menstrual status, chronic disease status, environmental endocrine disruptor exposure, and lifestyles. However, there are inevitable epidemiological bias in the existing studies, including recall bias, selection bias and measurement bias. Some methodological advances have brought new opportunities to TTP research, which make it possible to develop precision interventions for population fertility. Future TTP studies should take advantage of artificial intelligence, machine learning, and high-throughput sequencing technologies, and apply medical big data to fully consider and avoid possible bias in the design.

Conclusion

There are many opportunities and future challenges for TTP related studies which would provide a scientific basis for the “precise health management” of the population preparing for pregnancy.

As the problems of infertility and population aging increase, there is a growing interest in the factors that cause a decline in human fertility. Time-to-pregnancy (TTP) is a good indicator with which to reflect human fecundability, and a longer TTP is known to reflect a reduction in fertility. Many original studies, with different designs, have used TTP to explore the factors that might influence fertility, including basic demographic characteristics, chronic disease status, environmental endocrine disruptor exposure, and lifestyles. However, much of the existing evidence is inconsistent and limited by various types of bias. This review provides a synopsis of recent TTP studies, and highlights new opportunities and future challenges.

Patterns of environmental exposure to phenols in couples who plan to become pregnant

Phenols are widely used in consumer products and known for their reproductive toxicities. Little is known regarding the environmental exposure to phenols in couples prior to conception, a key period affecting fertility. We measured the urinary concentrations of six parabens and seven bisphenols in 903 pre-conception couples in China. We investigated the occurrence, distribution, source and health risk of phenols in husbands and wives separately, and the correlation and difference in phenol concentrations between couples. Similar distribution profiles of urinary phenols were observed between females and males. Methyl 4-hydroxybenzoate (MeP) and bisphenol A (BPA) were the predominant compounds. The level of urinary phenols in our population was mostly lower than the global levels. Exposure to phenols was linked to processed food and personal care products. The correlations between phenols in males and females were moderate (0.218-0.686), while the correlation in phenols between husband and wife was low (0.009-0.215). Female had a significantly higher urinary phenol levels than male (P < 0.05). Urinary phenols in couples were associated with family income, type of drinking water and frequency of household cleaning. Household factors accounted for ≤1.5% of variance in phenol levels between couples, suggesting that individual variations may be the major factor. Risk assessment showed that exposure to phenols posed a low hazard to 17.5% of the couples in our population. Our findings provide important evidence of environmental exposure to phenols in couples of child-bearing age.

Killing two birds with one stone: Pregnancy is a sensitive window for endocrine effects on both the mother and the fetus

Pregnancy is a complex process requiring tremendous physiological changes in the mother in order to fulfill the needs of the growing fetus, and to give birth, expel the placenta and nurse the newborn. These physiological modifications are accompanied with psychological changes, as well as with variations in habits and behaviors. As a result, this period of life is considered as a sensitive window as impaired functional and physiological changes in the mother can have short- and long-term impacts on her health. In addition, dysregulation of the placenta and of mechanisms governing placentation have been linked to chronic diseases later-on in life for the fetus, in a concept known as the Developmental Origin of Health and Diseases (DOHaD). This concept stipulates that any change in the environment during the pre-conception and perinatal (in utero life and neonatal) period to puberty, can be "imprinted" in the organism, thereby impacting the health and risk of chronic diseases later in life. Pregnancy is a succession of events that is regulated, in large part, by hormones and growth factors. Therefore, small changes in hormonal balance can have important effects on both the mother and the developing fetus. An increasing number of studies demonstrate that exposure to endocrine disrupting compounds (EDCs) affect both the mother and the fetus giving rise to growing concerns surrounding these exposures. This review will give an overview of changes that happen during pregnancy with respect to the mother, the placenta, and the fetus, and of the current literature regarding the effects of EDCs during this specific sensitive window of exposure.

Endocrine disrupting chemicals and reproductive disorders in women, men, and animal models

This chapter covers the known effects of endocrine disrupting chemicals (EDCs) on reproductive disorders. The EDCs represented are highly studied, including plasticizers (bisphenols and phthalates), chemicals in personal care products (parabens), persistent environmental contaminants (polychlorinated biphenyls), and chemicals in pesticides or herbicides. Both female and male reproductive disorders are reviewed in the chapter. Female disorders include infertility/subfertility, irregular reproductive cycles, early menopause, premature ovarian insufficiency, polycystic ovarian syndrome, endometriosis, and uterine fibroids. Male disorders include infertility/subfertility, cryptorchidism, and hypospadias. Findings from both human and animal studies are represented.

Adverse reproductive function induced by maternal BPA exposure is associated with abnormal autophagy and activating inflamation via mTOR and TLR4/NF-κB signaling pathways in female offspring rats

Bisphenol A (BPA) can affect reproductive function, but its mechanism of reproductive toxicity is unclear, and the effect of BPA on the onset of puberty was inconsistent. The main purpose of this study is to investigate the effects of perinatal exposure to BPA on the onset of puberty and reproductive function, and its mechanism from the aspect of autophagy and inflammation in ovarian and uterus tissues of female offspring. Twenty-one pregnant SD rats were randomly divided into three groups: Control group, 1 μg/mL BPA (LBPA) and 10 μg/mL BPA group (HBPA) via drinking water from gestational day 6 to the end of lactation. After weaning, female offspring rats were fed a normal diet and drinking water for 5 weeks. The levels of E2, LH, FSH, T, and IL-6 and TNF-α, and the onset of puberty, and morphological changes in ovarian and uterine were determined in female offspring at 8 weeks. The levels of TLR4, NF-κB, PI3K/Akt/mTOR and autophagy related protein in uterine tissue were also detected. Our results indicated that perinatal exposure to BPA advanced puberty, which was associated with increased serum E2, LH and FSH levels. There was a significantly thin endometrium epithelium in HBPA group compared with control group, which may affect reproductive function. The adverse effect of perinatal BPA exposure on reproductive function maybe was associated with the activation of inflammation and abnormal autophagy via TLR4/NF-κB and mTOR signaling pathways respectively in female offspring.