Does early growth influence timing of the menopause? Evidence from a British birth cohort.

BACKGROUND Few adult environmental or behavioural factors have been consistently associated with age at menopause. The peak number of follicles attained in utero or lost before ovulation begins may be more important. This study investigates whether birthweight, childhood body size, having been breastfed and early socioeconomic circumstances are associated with age at menopause. METHODS Menopausal status and risk factor information have been collected prospectively from 1572 British women followed up since their birth in 1946, so far until 53 years. Cox's regression models were used to investigate the relationships between early life factors and rate of menopause. RESULTS Age at menopause varied by duration of breastfeeding, weight at age 2 years, childhood socioeconomic status, but not birthweight. In a multiple regression model, women of low weight at 2 years had an earlier menopause [hazard ratio (HR) = 0.75 for highest versus lowest quarter: 95% confidence interval (CI) 0.54-1.02] and those who had been breastfed had a later menopause (HR = 0.69 for vertical line 7 months versus never breastfed: 95% CI 0.51-0.92) than others. The influence of socioeconomic status was attenuated. CONCLUSIONS Early life influences may influence ovarian ageing, highlighting the importance of investigating factors from across the life course.