Association of In Utero Exposures With Risk of Early Natural Menopause

Endocrine-disrupting chemicals and female reproductive health: a growing concern

Female fertility and reproductive health depend on a series of developmental steps from embryogenesis through puberty, in addition to the proper functioning of the reproductive system in adulthood. Two important steps are the establishment of the ovarian reserve and development of the hypothalamic-pituitary-ovarian axis. During reproductive years, maintaining an adequate ovarian reserve of follicles as well as balanced neuroendocrine control of reproductive organs is crucial for fertility. Dysregulation of either of these events, during development or in adulthood, can lead to reproductive disorders. Over the past five decades, human fertility rates have declined, whereas the incidence of female reproductive disorders has risen, trends partially linked to environmental factors such as exposure to endocrine-disrupting chemicals (EDCs). Here we outline epidemiological and mechanistic evidence for how EDCs affect the ovarian reserve during early development, its maintenance during adulthood and the establishment of the hypothalamic-pituitary control of puberty and ovulation. Our Review not only reveals strong support for the role of EDC exposure in the development of female reproductive disorders such as abnormal puberty, impaired fertility, premature menopause or polycystic ovarian syndrome, but also highlights knowledge gaps, including the difficulty to prove causality between exposure and human disease manifestation.

Endocrine-disrupting chemicals and reproductive health: With focus on the developmental window of susceptibility

Sexual differentiation is highly dependent on the fetal hormonal environment, guiding sexual development and establishing the foundation for lifelong reproductive health. This short communication highlights critical windows of sex determination and differentiation, emphasizing the role of steroid sex hormones, alongside other factors, in orchestrating these processes in early life. Growing evidence suggests that endocrine-disrupting chemicals (EDCs) can disrupt these tightly regulated pathways, leading to developmental disturbances that manifest as reproductive disorders at birth or later in life. In males, disrupted androgen signaling during fetal development is linked to hypospadias, cryptorchidism, reduced fertility, and testicular cancer, while in females, EDC exposure may contribute to altered ovarian function, early puberty, polycystic ovary syndrome (PCOS), and infertility. By illustrating how EDCs can interfere with sexual development, this brief review underscores the need for further research and regulatory measures to mitigate their impact on human health.

Evolutionary Perspectives, Comparative Approaches, and the Lived Experience of Menopause

The purpose of this synthesis is to review age at menopause, symptom experience at midlife, and the evolution of menopause in a way that is helpful for biological anthropologists who are interested in the study of this challenging time of life. The synthesis begins with the biology of menopause, then shifts to the evolution of menopause with an emphasis on phylogenetic and adaptationist perspectives. Discussion of the biology and evolution of menopause incorporates a cross-species perspective, with particular attention to whales and primates. The synthesis continues with a cross-population review of variation in age at menopause. The final section is about symptom experience across populations with attention to the medical context of midlife, a focus on hot flashes, and consideration of the strengths and limitations of ethnographic and questionnaire-based research. The review ends with suggestions for where biological anthropology can make important contributions to the research of midlife and menopause.

Mediation of the effect of prenatal maternal smoking on time to natural menopause in daughters by birthweight-for-gestational-age z-score and breastfeeding duration: analysis of two UK birth cohorts born in 1958 and 1970

BACKGROUND

Prenatal maternal smoking, lower birthweight, and shorter breastfeeding duration have all been associated with an earlier age at menopause in daughters. We estimated the extent to which birthweight-for-gestational-age z-score and breastfeeding duration mediate the effect of prenatal maternal smoking on time to natural menopause in daughters.

METHODS

Using pooled data from two prospective birth cohort studies - the 1970 British Cohort Study (n = 3,878) followed-up to age 46 years and the 1958 National Child Development Study (n = 4,822) followed-up to age 50 years - we perform mediation analysis with inverse odds weighting implemented in Cox proportional-hazards models.

RESULTS

Prenatal maternal smoking was associated with lower birthweight z-scores [β: -0.29; 95% CI -0.34, -0.24] and reduced breastfeeding duration [RRR< 1month: 0.90; 95% CI 0.79, 1.02; RRR≥ 1 month: 0.66; 95% CI 0.59, 0.73 relative to women who were never breastfed]. Greater z-score for birthweight [HR: 0.96; 95% CI 0.91, 1.01] and longer breastfeeding duration [HR≥ 1 month: 0.84; 95% CI 0.74, 0.96] were associated with lower hazards for earlier age at natural menopause. The total effect of prenatal maternal smoking on the time to natural menopause in daughters was estimated as a HR of 1.13 [95% CI 1.02, 1.24]. Birthweight z-score and breastfeeding duration jointly explained an estimated 14% of the total effect [HRNIE: 1.02; 95% CI 0.99, 1.05].

CONCLUSIONS

The consequences of smoking during pregnancy on the earlier experience of natural menopause in daughters may partly be offset by intrauterine growth and longer breastfeeding duration to the extent that they mediate the risk of earlier menopause. However, since the extent of mediation by birthweight z-score and breastfeeding duration is small, other factors, including the direct effect of maternal smoking in utero, may play a more important role.

Evolutionary Perspectives, Comparative Approaches, and the Lived Experience of Menopause

The purpose of this synthesis is to review age at menopause, symptom experience at midlife, and the evolution of menopause in a way that is helpful for biological anthropologists who are interested in the study of this challenging time of life. The synthesis begins with the biology of menopause, then shifts to the evolution of menopause with an emphasis on phylogenetic and adaptationist perspectives. Discussion of the biology and evolution of menopause incorporates a cross-species perspective, with particular attention to whales and primates. The synthesis continues with a cross-population review of variation in age at menopause. The final section is about symptom experience across populations with attention to the medical context of midlife, a focus on hot flashes, and consideration of the strengths and limitations of ethnographic and questionnaire-based research. The review ends with suggestions for where biological anthropology can make important contributions to the research of midlife and menopause.

Associations between birthweight and preterm birth and the ages at menarche and menopause

BACKGROUND

Women who reach menarche and menopause at earlier ages have been shown to be at increased risk for numerous conditions including cardiovascular disease, cancer, depression, and obesity; however, risk factors for earlier ages of menarche and menopause are not fully understood. Therefore, we aimed to perform a retrospective investigation of the associations between a personal birthweight and/or being born preterm and the age of and menarche and menopause and related events in the Women's Health Initiative, a large, racially and ethnically diverse cohort of postmenopausal women.

METHODS

At study entry, women reported their birthweight by category (< 6 lbs., 6-7 lbs. 15 oz, 8-9 lbs. 15 oz, or ≥ 10 lbs.) and preterm birth status (4 or more weeks premature). Ages at events related to menarche and menopause were also self-reported. Linear regression and logistic regression models were used to estimate unadjusted and adjusted effect estimates (β) and odds ratios (OR), respectively (n ≤ 86,857). Individuals born preterm were excluded from all birthweight analyses.

RESULTS

After adjustments, individuals born weighing < 6lbs. were more likely to reach natural menopause at an earlier age (adjusted β=-0.361, SE = 0.09, P = < 0.001) and have a shorter reproductive window (adjusted β = -0.287, SE = 0.10, p < 0.004) compared to individuals weighing 6-7 lbs. 15 oz. Individuals born preterm were also more likely to reach natural menopause at an earlier age (adjusted β=-0.506, SE = 0.16, P = 0.001) and have a shorter reproductive window (adjusted β = -0.418, SE = 0.17, p < 0.006).

CONCLUSIONS

These findings raise concerns that, as more preterm and low birthweight individuals survive to adulthood, the prevalence of earlier-onset menarche and menopause may increase. Clinical counseling and interventions aimed at reducing the incidence of preterm and low birthweight births, as well as intensification of lifestyle modifications to reduce CVD risk among women with these early-life risk factors, should be prioritized.

Birth weight and premature ovarian insufficiency: a systematic review and meta-analysis

OBJECTIVE

To comprehensively evaluate the effect of low birth weight on premature ovarian insufficiency.

METHODS

We performed a systematic review of the literature by searching MEDLINE, EMBASE, Web of Science, Scopus, Wanfang and CNKI up to August 2023. All cohort and case-control studies that included birth weight as an exposure and premature ovarian insufficiency as an outcome were included in the analysis. Data were combined using inverse-variance weighted meta-analysis with fixed and random effects models and between-study heterogeneity evaluated. We evaluated risk of bias using the Newcastle Ottawa Scale and using Egger's method to test publication bias. All statistical analyses were performed with the use of R software.

RESULTS

Five articles were included in the review. A total of 2,248,594 women were included, including 21,813 (1%) cases of premature ovarian insufficiency, 150,743 cases of low birth weight, and 220,703 cases of macrosomia. We found strong evidence that changed the results of the previous review that low birth weight is associated with an increased risk of premature ovarian insufficiency (OR = 1.15, 95%CI 1.09-1.22) in adulthood compared with normal birth weight. No effect of macrosomia on premature ovarian insufficiency was found.

CONCLUSIONS

Our meta-analysis showed strong evidence of an association between low birth weight and premature ovarian insufficiency. We should reduce the occurrence of low birth weight by various methods to avoid the occurrence of premature ovarian insufficiency.