Several early-life exposures were associated with greater than 10% relative increases in the occurrence of early or late menarche. Exposures associated with early menarche were having had a teenage mother, being firstborn, having low birth weight, having been born at least one month early, having been fed soy formula, and several maternal factors during the index pregnancy (diabetes, hypertensive disorder, DES use, and smoking) (Table 2). An association was found only with pre-pregnancy diabetes and not with gestational diabetes, whereas associations were similar for the two types of pregnancy-related hypertensive disorders. Associations were generally stronger for very early menarche (≤10 years) than for menarche at 11 years. In particular, associations were found specific to very early menarche for three exposures (DES, rRR = 1.56 [95% CI = 1.24-1.96]; firstborn, 1.18 [1.06-1.32]; and soy formula, 1.21 [0.94-1.54]). Soy formula consumption was also associated with late menarche. Associations with late menarche for having been born at least one month early and multiple birth were specific to very late menarche (≥15 years).
