Age at menarche and first pregnancy among psychosocially at-risk adolescents.

We sought to determine which factors influence the association between menarche and conception among adolescent study participants (n = 1030), who demonstrated an earlier age of menarche than did national samples. Age at first sexual intercourse (coitarche) mediated the relationship between age at menarche and first pregnancy among White girls, whereas gynecologic age at coitarche (age at coitarche minus age at menarche) and age at menarche explained the timing of the first pregnancy among Black and Hispanic girls. Pregnancy prevention interventions to delay coitarche should also include reproductive education and contraception.