Effects of maternal smoking on offspring reproductive outcomes: an intergenerational study in the North East of Scotland

Intergenerational trends in reproduction: Infertility and pregnancy loss

This review article summarises the evidence for intergenerational trends observed to date within infertility and pregnancy loss. There appears to be evidence of intergenerational trends between mothers and daughters for the age at menopause, endometriosis, polycystic ovarian syndrome (PCOS), male factor infertility and miscarriage. At present, there is no evidence for a predisposition to stillbirth between mothers and daughters. One study found an association with familial predisposition for ectopic pregnancy. Very few studies have considered the potential for paternal transmission of risk of infertility or pregnancy loss. The majority of studies to date have significant limitations because of their observational design, risk of recall bias and risk of confounding. Therefore, high-quality well-designed research, with multi-centre collaboration and utilisation of registry-based data sources and individual patient data, is needed to understand whether infertility and pregnancy loss may have heritable factors. Epidemiological findings need to be followed up and investigated with translational research to determine the possible causalities as well as any implications for clinical practice.

The Impact of Early-Life Exposures on Women's Reproductive Health in Adulthood

Purpose of Review

To review the effects of early-life, preconception, and prior-generation exposures on reproductive health in women.

Recent Findings

Women’s early-life factors can affect reproductive health by contributing to health status or exposure level on entering pregnancy. Alternately, they can have permanent effects, regardless of later-life experience. Nutrition, social class, parental smoking, other adverse childhood experiences, environmental pollutants, infectious agents, and racism and discrimination all affect reproductive health, even if experienced in childhood or in utero. Possible transgenerational effects are now being investigated through three- or more-generation studies. These effects occur with mechanisms that may include direct exposure, behavioral, endocrine, inflammatory, and epigenetic pathways.

Summary

Pregnancy is increasingly understood in a life course perspective, but rigorously testing hypotheses on early-life effects is still difficult. In order to improve the health outcomes of all women, we need to expand our toolkit of methods and theory.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40471-021-00279-0.

Testing the twin testosterone transfer hypothesis-intergenerational analysis of 317 dizygotic twins born in Aberdeen, Scotland

STUDY QUESTION

Does having a male co-twin influence the female twin's reproductive outcomes?

SUMMARY ANSWER

Women with a male co-twin had the same chances of being pregnant and having children compared to same-sex twin pairs.

WHAT IS KNOWN ALREADY

According to the twin testosterone transfer (TTT) hypothesis, in an opposite-sex twin pregnancy, testosterone transfer from the male to the female co-twin occurs. A large body of literature supports the negative impact of prenatal testosterone exposure on female's reproductive health in animal models; however, evidence from human studies remains controversial.

STUDY DESIGN, SIZE, DURATION

This cohort study included all dizygotic female twins in the Aberdeen Maternity and Neonatal Databank (Scotland) born before 1 January 1979. The 317 eligible women were followed up for 40 years for any pregnancies and the outcome of those pregnancies recorded in the same database.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Fertility outcomes (number of pregnancies, number of livebirths and age at first pregnancy) were compared between women with a male co-twin (exposed group, n = 151) and those with a female co-twin (unexposed group, n = 166). Population averaged models were used to estimate odds ratios (OR) and 95% CI for all outcomes with adjusting for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

There were no differences in chances of having pregnancies (adj. OR 1.33; 95% CI 0.72, 2.45) and livebirths (adj. OR 1.22; 95% CI 0.68, 2.18) between women from same-sex and opposite-sex twin pairs. Women with a male co-twin were more likely to smoke during pregnancy and, in the unadjusted model, were younger at their first pregnancy (OR 2.13; 95% CI 1.21, 3.75). After adjusting for confounding variables (year of birth and smoking status) the latter finding was no longer significant (OR 1.67; 95% CI 0.90, 3.20).

LIMITATIONS, REASONS FOR CAUTION

The dataset was relatively small. For women without a pregnancy recorded in the databank, we assumed that they had not been pregnant.

WIDER IMPLICATIONS OF THE FINDINGS

Despite the evidence from animal studies concerning the adverse effects of prenatal testosterone exposure on female health, our results do not support the TTT hypothesis. The finding that women with a male co-twin are more likely to smoke during pregnancy highlights the importance of considering post-socialisation and social effects in twin studies.

STUDY FUNDING/COMPETING INTEREST(S)

European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie project PROTECTED (grant agreement No. 722634) and FREIA project (grant agreement No. 825100). No competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Recalled maternal lifestyle behaviors associated with anti-müllerian hormone of adult female offspring

Anti-müllerian hormone (AMH) is an established marker of ovarian reserve that decreases with age. Though the pool of ovarian follicles is established during fetal development, impacts of in utero exposures on AMH are uncertain. Thus, we sought to evaluate associations of in utero exposures with AMH of adult daughters with a prospective cohort study of adult daughters at university medical centers. Women noted their mother's reported use of diethylstilbestrol (DES), vitamins, tobacco, alcohol, and caffeine during pregnancy, and their mother's occupation during pregnancy. All participants were reproductive age women (18-40 years) enrolled in the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial. Serum AMH concentrations were measured at baseline prior to conception and categorized using clinical guidelines. Multinomial regression models estimated associations between each exposure and high (>3.5 ng/mL) and low (<1.0 ng/mL) versus normal AMH (1.0-3.5 ng/mL), adjusting for participant's age, mother's age, mother's history of fertility treatment, and mother's use of vitamins. In 1202 women with available data, maternal caffeine use was associated with an increased risk of low AMH, compared to normal (relative risk [RR] 1.90, 95 % confidence interval [CI] 1.09, 3.30). Vitamins were associated with an increased risk of high AMH compared to normal (RR 1.93, 95 % CI 1.24, 3.00). Other exposures were not associated with AMH concentrations in offspring. Maternal caffeine and vitamin use during pregnancy may be associated with ovarian reserve in adult offspring, highlighting the potential importance of pregnancy lifestyle on the reproductive health of daughters.

Family history and risk of miscarriage: A systematic review and meta-analysis of observational studies

INTRODUCTION

Miscarriage, a spontaneous pregnancy loss at <24 weeks' gestation, is a common complication of pregnancy but the etiologies of miscarriage and recurrent miscarriage are not fully understood. Other obstetric conditions such as preeclampsia and preterm birth, which may share similar pathophysiology to miscarriage, exhibit familial patterns, suggesting inherited predisposition to these conditions. Parental genetic polymorphisms have been associated with unexplained miscarriage, suggesting there could be a genetically inherited predisposition to miscarriage. This systematic review and meta-analysis of observational studies aimed to assess the association between family history of miscarriage and the risk of miscarriage in women.

MATERIAL AND METHODS

A systematic review and meta-analysis of observational studies was carried out in accordance with Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. Electronic searches using databases (MEDLINE, EMBASE and CINAHL) were carried out to identify eligible studies from 1946 until 2019. Observational studies (cohort or case-control) were included. Human studies only were included. Participants were women of reproductive age. Exposure was a family history of one or more miscarriage(s). The primary outcome was miscarriage in women. Abstracts were screened and data were extracted by two independent reviewers. Study quality was assessed using Critical Appraisal Skills Program (CASP) tools. Data were pooled from individual studies using the Mantel-Haenszel method to produce pooled odds ratios (ORs) with 95% confidence intervals (95% CI). Systematic review registration number (PROSPERO): CRD42019127950.

RESULTS

Thirteen studies were identified in the systematic review; 10 were eligible for inclusion in the meta-analysis. Twelve studies reported an association between family history of miscarriage and miscarriage in women. In all, 41 287 women were included in the meta-analysis. Women who miscarried were more likely to report a family history of miscarriage (pooled unadjusted OR 1.90, 95% CI 1.37-2.63). Overall study quality and size varied, with few adjusting for confounding factors. Results should be interpreted with caution as the associations presented are based on unadjusted analyses only.

CONCLUSIONS

Women who miscarry may be more likely to have a family history of miscarriage. Further research is required to confirm or refute the findings.