Age at menarche and subsequent reproductive events.

A woman's age at menarche may be related to later reproductive performance, including age at first birth and risk of spontaneous abortion. This paper presents data from 2062 women with 4477 pregnancies in the Menstrual and Reproductive Health Study, a prospective study which has been in progress since 1935. Age at menarche is directly related to the age at which a woman marries and conceive a first child, but is unrelated to total fertility, frequency of induced abortion, or risk of stillbirth. Women with either early or late menarche are significantly more likely to have had an ectopic pregnancy. Overall spontaneous abortion risk declines slightly with increasing age at menarche. This trend is not seen, however, when first pregnancies alone are considered. This suggests that the overall trend with age at menarche is not related to a woman's underlying spontaneous abortion risk but rather to unknown selective factors. Women who were very young (less than 11 years) at menarche differ from the others with regard to many measures of reproductive performance. However, these women represent only a small proportion of the total study group.