Age at menarche, at first intercourse, and at first pregnancy

Data from an urban sample of American women of reproductive ages demonstrate that age at menarche is correlated with age at first intercourse, that age at first intercourse is correlated with age at first pregnancy, and that menarche is therefore correlated with age at first pregnancy. This applied to both blacks and whites when examined for the early years of the reproductive cycle. Girls with early menarche, compared to those with late menarche, are more than twice as likely to have had intercourse by age 16, and almost twice as likely to have given birth or had a pregnancy terminated by age 18. It is therefore useful to think of the timing of menarche as an indicator of the probability of early intercourse and early childbearing.