The association of birth interval, maternal age and season of birth with the fertility of daughters: a retrospective cohort study based on family reconstitutions from nineteenth and early twentieth century Quebec

Risk factors for natural menopause before the age of 45: evidence from two British population-based birth cohort studies

Background

Menopause that occurs before the age of 45 and is not medically induced (referred to here as ‘early natural menopause’) affects around one in 10 women and has serious health consequences. These consequences include increased risk of all-cause mortality, cardiovascular disease, osteoporosis, and type 2 diabetes.

Methods

We investigate risk factors for the onset of natural menopause before the age of 45 in two population-based prospective cohort studies in Britain: the 1958 cohort following 8959 women and the 1970 cohort following 8655 women. These studies follow women from birth to adulthood, and we use harmonized data on birth and early life characteristics, reproductive health, health behaviour, and socioeconomic characteristics for 6805 women who were pre-menopausal, peri-menopausal or had undergone natural menopause. Of these 6805 women, 3614 participated in the 1958 cohort (of which 368 had early menopause) and 3191 participated in the 1970 cohort (of which 206 had early menopause). Taking a life course approach, we focus on three distinct life stages - birth/early life, childhood, and early adulthood - to understand when risk factors are most harmful. Respecting the temporal sequence of exposures, we use a series of multivariable logistic regression models to estimate associations between early menopause and each potential risk factor adjusted for confounders.

Results

We find that early menopause is influenced by circumstances at birth. Women born in lower social class families, whose mother smoked during the pregnancy or who were breastfed 1 month or less were more likely to undergo early menopause. Early menopause is also associated with poorer cognitive ability and smoking in childhood. Adult health behaviour also matters. Smoking is positively correlated with early menopause, while regular exercise and moderate frequency of alcohol drinking in women’s early thirties are associated with reduced risk of early menopause. The occurrence of gynaecological problems by women’s early thirties is also linked to early menopause.

Conclusions

We demonstrate that characteristics at different periods of life are associated with early menopause. Some of these associations relate to modifiable behaviours and thus the risks of early menopause and the adverse health outcomes associated with it may be preventable.

Maternal age at birth and daughter's fecundability

STUDY QUESTION

Do daughters of older mothers have lower fecundability?

SUMMARY ANSWER

In this cohort study of North American pregnancy planners, there was virtually no association between maternal age ≥35 years and daughters' fecundability.

WHAT IS KNOWN ALREADY

Despite suggestive evidence that daughters of older mothers may have lower fertility, only three retrospective studies have examined the association between maternal age and daughter's fecundability.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study of 6689 pregnancy planners enrolled between March 2016 and January 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pregnancy Study Online (PRESTO) is an ongoing pre-conception cohort study of pregnancy planners (age, 21-45 years) from the USA and Canada. We estimated fecundability ratios (FR) for maternal age at the participant's birth using multivariable proportional probabilities regression models.

MAIN RESULTS AND THE ROLE OF CHANCE

Daughters of mothers ≥30 years were less likely to have previous pregnancies (or pregnancy attempts) or risk factors for infertility, although they were more likely to report that their mother had experienced problems conceiving. The proportion of participants with prior unplanned pregnancies, a birth before age 21, ≥3 cycles of attempt at study entry or no follow-up was greater among daughters of mothers <25 years. Compared with maternal age 25-29 years, FRs (95% CI) for maternal age <20, 20-24, 30-34, and ≥35 were 0.72 (0.61, 0.84), 0.92 (0.85, 1.00), 1.08 (1.00, 1.17), and 1.00 (0.89, 1.12), respectively.

LIMITATIONS, REASONS FOR CAUTION

Although the examined covariates did not meaningfully affect the associations, we had limited information on the participants' mother. Differences by maternal age in reproductive history, infertility risk factors and loss to follow-up suggest that selection bias may partly explain our results.

WIDER IMPLICATIONS OF THE FINDINGS

Our finding that maternal age 35 years or older was not associated with daughter's fecundability is reassuring, considering the trend towards delayed childbirth. However, having been born to a young mother may be a marker of low fecundability among pregnancy planners.

STUDY FUNDING/COMPETING INTEREST(S)

PRESTO was funded by NICHD Grants (R21-HD072326 and R01-HD086742) and has received in-kind donations from Swiss Precision Diagnostics, FertilityFriend.com, Kindara.com, and Sandstone Diagnostics. Dr Wise is a fibroid consultant for AbbVie, Inc.

TRIAL REGISTRATION NUMBER

n/a.

Maternal age at birth and daughters' subsequent childlessness

STUDY QUESTION

Does maternal age at a daughter's birth predict her subsequent probability of lifelong childlessness?

SUMMARY ANSWER

In this study population, women born to older mothers were more likely to be childless.

WHAT IS KNOWN ALREADY

Although maternal age at childbearing is increasing in many countries, there is limited evidence on whether being born to older parents may influence offspring fertility.

STUDY DESIGN SIZE AND DURATION

This analysis included 43 135 women from the US-based Sister Study, a cohort study of 50 884 sisters of women with breast cancer recruited between 2003 and 2009.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants had no breast cancer at baseline. Women were included in the analytic sample if they were born between 1930 and 1964 and were at least 44 years old at enrolment. Median age when reproductive history was last ascertained was 63.8 years. We estimated relative risks (RR) and 95% CI of lifelong childlessness as a function of maternal age at birth, using multivariable log-binomial models, including total number of siblings, birth order, socioeconomic indicators of the family of origin, race and birth cohort. We examined the association in different subgroups and in a sibling-matched analysis including 802 sister pairs discordant for childlessness.

MAIN RESULTS AND ROLE OF CHANCE

Compared with women born to 20-24-year-old mothers, those born to mothers aged 25-29, 30-34 and ≥35 years were more likely to be childless [RR (95% CI): 1.21 (1.14-1.29), 1.30 (1.22-1.39) and 1.40 (1.31-1.50), respectively]. The association was consistent in strata defined by birth cohort, number of siblings, birth order, and participant's educational level, as well as within sister pairs. Overall, we found weak evidence for an independent contribution of paternal age at birth to the daughter's probability of childlessness.

LIMITATIONS REASONS FOR CAUTION

All participants had at least one sister, and all information was self-reported. We had no knowledge of whether childlessness was intentional and found only a modest association between maternal age at birth and self-reported indicators of infertility. Still, the association with childlessness was highly consistent.

WIDER IMPLICATIONS OF THE FINDING

Given the widespread tendency to delay childbearing, evaluating the influence of maternal age at birth on offspring fertility is a public health priority.

STUDY FUNDING/COMPETING INTERESTS

This research was supported in part by the Intramural Research Programme of the NIH, National Institute of Environmental Health Sciences (Z01-ES044005). The authors report no conflict of interest.

Evidence for sexually dimorphic associations between maternal characteristics and anogenital distance, a marker of reproductive development

Data from animal models, historical cohorts, and modern epidemiologic studies have suggested that maternal characteristics can affect reproductive health of offspring; however, distinguishing between prenatal and postnatal contributions is difficult. Anogenital distance (AGD), the distance from the anus to the genitals, is believed to be a biomarker of prenatal androgen exposure in many species, and in humans it has been associated with several adult reproductive health outcomes. We used data from a pregnancy cohort study conducted in 4 US cities from 1999-2005 to examine whether AGD measurements in infants were associated with maternal self-reported age at conception, age at menarche, age at first birth, parity, and gravidity. AGD was measured in 289 infants (140 male, 149 female) born to study participants. After adjustment for relevant covariates, in linear regression models stratified by infant sex, maternal age was positively associated with AGD in male infants (AGD, anus to penis: β = 0.50, P = 0.002; AGD, anus to scrotum: β = 0.29, P = 0.02) but not female infants. Parity was inversely associated with AGD (anus to scrotum; β = -1.68, P = 0.03) in male infants. No other maternal characteristic predicted AGD in either sex. The mechanism underlying the unexpected relationship between maternal characteristics and AGD is unknown; however, we suggest several possibilities for future study.

The association between interpregnancy interval and birth weight: what is the role of maternal polyunsaturated fatty acid status?

Background

The objective of this study was to evaluate the mediating role of maternal early pregnancy plasma levels of long chain polyunsaturated fatty acids (LCPUFAs) in the association of interpregnancy interval (IPI) with birth weight and smallness for gestational age (SGA) at birth.

Methods

We analysed a subsample of the Amsterdam Born Children and their Development (ABCD) cohort, comprising 1,659 parous pregnant women recruited between January 2003 and March 2004. We used linear and logistic regression to evaluate the associations between fatty acid status, interpregnancy interval and pregnancy outcome.

Results

Low plasma phospholipids concentrations of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and dihomo-gamma-linolenic acid (DGLA), and high concentrations of arachidonic acid (AA) during early pregnancy were associated with reduced birth weight and/or an increased risk of SGA. Short IPIs (< 6 months, with 18–23 months as a reference) were associated with a mean decrease of 207.6 g (SE: ± 73.1) in birth weight (p = 0.005) and a twofold increased risk of SGA (OR: 2.05; CI: 0.93–4.51; p = 0.074). Adjustment for maternal fatty acid concentrations did not affect these results to any meaningful extent.

Conclusions

Despite the observed association of maternal early pregnancy LCPUFA status with birth weight and SGA, our study provides no evidence for the existence of an important role of maternal EPA, DHA, DGLA or AA in the association of short interpregnancy intervals with birth weight and SGA.

Advanced maternal age, short interpregnancy interval, and perinatal outcome

OBJECTIVE

The purpose of this study was to evaluate whether the association between short interpregnancy intervals and perinatal outcome varies with maternal age.

STUDY DESIGN

We performed a retrospective cohort study among 263,142 Dutch women with second deliveries that occurred between 2000 and 2007. Outcome variables were preterm delivery (<37 weeks of gestation), low birthweight in term deliveries (<2500 g) and small-for-gestational age (<10th percentile for gestational age on the basis of sex- and parity-specific Dutch standards).

RESULTS

Short interpregnancy intervals (<6 months) was associated positively with preterm delivery and low birthweight, but not with being small for gestational age. The association of short interpregnancy interval with the risk of preterm delivery was weaker among older than younger women. There was no clear interaction between short interpregnancy interval and maternal age in relation to low birthweight or small for gestational age.

CONCLUSION

The results of this study indicate that the association of short interpregnancy interval with preterm delivery attenuates with increasing maternal age.

Season of birth and subsequent body size: the potential role of prenatal vitamin D

OBJECTIVES

The relationship between season of birth and various physical and psychological outcomes was reported in many studies, although the underlying mechanism still remains unrecognized. The aim of this study was to explore the season-of-birth effect on body size in the sample of 1,148 eight-year-old Polish urban children and propose the mechanism responsible for this effect.

METHODS

The children were examined three times at their birthdays and at two cross-sectional surveys. Effects of the season of birth were checked by fitting the cosine function to empirical values and by comparison between two groups born in different periods of the year.

RESULTS

Data gathered at three examinations led to the same results: season-of-birth effect occurred only in boys and only in those relatively shortly breastfed and/or descended from the families of low-socioeconomic status. Specifically, the individuals born in October-April were taller (by 2-3 cm), heavier (by 2-3 kg), and fatter than those born in May-September.

CONCLUSIONS

The following explanatory mechanism has been formulated: insolation in Poland is minimal in November-February (winter period), and so ultraviolet absorption and vitamin D production is then the lowest. Vitamin D regulates embryo's cellular differentiation, and its deficiency triggers permanent developmental changes. Therefore, individuals conceived in autumn (i) are at the greatest risk of early vitamin D deficiency, (ii) are born in summer, and (iii) are relatively small in their further lives. The contribution of low-socioeconomic status, short breastfeeding, and being a male to the occurrence of the season-of-birth effect is also discussed.

Antral follicle counts are related to age at natural fertility loss and age at menopause

OBJECTIVE

The variability in ultrasound-based antral follicle counts sized 2-10 mm after allowing for age-related decline is considerable. This may represent differences in actual reproductive age among women. This hypothesis was tested by cohort comparison for distribution of age at occurrence of reproductive events.

DESIGN

A model with a nonlinear mean decline with age was fitted to antral follicle counts (AFC) obtained in 163 regularly cycling fertile volunteers. Ages at last child birth and menopause were predicted from the individual AFC by using thresholds to represent these events and the model for decline with age. Distributions of the observed ages at last childbirth (proxy variable for loss of natural fertility) and ages at menopause were obtained from the BALSAC demographic database and the Prospect-EPIC study, respectively. The observed distributions were compared with the predicted distributions by using visual comparison and quantile-quantile plots. Predictions of age at last child and age at menopause were done using percentiles of the modeled AFC distribution for given age, and corresponding percentiles of the predicted distributions of age at these reproductive events, with predictions following from the position of a woman's AFC relative to these percentiles.

RESULTS

The predicted distributions of age at last child and age at menopause showed good agreement with the observed distributions in the BALSAC and EPIC cohort. Compared with age alone, antral follicle counts gave some additional information for individual prediction of age at last child and menopause.

CONCLUSIONS

The link between declining antral follicle counts and reproductively significant events like loss of natural fertility and menopause is strengthened by the high degree of similarity among the predicted and observed age distributions. Predictive usefulness of this relationship in a clinical setting may be more marginal, except in the case of women who have low AFCs for their age.

Delayed motherhood increases the probability of sons to be infertile

PURPOSE

To ascertain whether advanced maternal age at birth is associated with offspring infertility.

METHODS

A written questionnaire was completed by infertile couples attending our clinic in the presence of a researcher.

RESULTS

Maternal age at birth (odds ratio 1.236, 95% CI 1.100-1.388) and birth order of all respondents and their respective siblings (odds ratio 0.551, 95% CI 0.351-0.865) were significant predictors of male infertility. The probability of a man being infertile increased as mother's age at birth increased (regression coefficient +/- standard error 0.212 +/- 0.059; P < 0.001), but decreased as birth order increased (regression coefficient +/- standard error -0.596 +/- 0.230; P = 0.010).

CONCLUSIONS

Delayed motherhood may enhance the probability of sons to be infertile. The probability of a man being infertile would be greater if he comes from a small family than if he comes from a large family.