Early onset of puberty, which has often been approximated by young age at menarche, can have important implications for conditions diagnosed later in life, such as breast cancer and cardiovascular disease.2 Furthermore, animal studies have shown that prenatal and neonatal exposure to exogenous estrogens can alter pubertal timing.26-28 We found that several early-life exposures were associated with early menarche: low birth weight, young maternal age at the index birth, firstborn status, soy formula, and maternal exposures during the index pregnancy (pre-pregnancy diabetes, pregnancy-related hypertensive disorder, smoking, and DES use). Associations with low birth weight, pre-pregnancy diabetes, pregnancy-related hypertensive disorder, in utero DES, firstborn status, and soy formula were stronger for very early menarche (≤10 years) than for menarche at 11 years. Soy formula, multiple birth, and having been born at least one month early were the only exposures associated with late menarche.
