Menarche: target age for reinforcing sex education for adolescents.

Teenage sexual activity has led to an increasing prevalence of pregnancy and sexually transmitted disease in this age group. Attempts at prevention should begin with education. This study compares the ages of menarche with ages of first intercourse among adolescent females in 1971 and 1976, stratified by ethnic group and residence (urban versus rural). Findings demonstrated that an earlier age at menarche is consistently associated with earlier intercourse. Menarche should therefore be used as a target age for reinforcing and expanding adolescent females' knowledge of risks associated with sexual intercourse.