Several studies have identified explicative factors for adolescents' sexual risk behaviors and related outcomes such as unintended pregnancy; however, less is known about the mechanisms through which such factors act. Our study explored the role of female education and partner age difference as explicative mechanisms of the association between age at first sexual intercourse (AFSI) and unintended pregnancy while controlling for the role of other contextual factors (i.e., socioeconomic status,

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... hnicity, religious beliefs, and place of residence) and sexual-related mechanisms (i.e., number of sexual partners) that are known to be associated with adolescent pregnancy. The sample consisted of 613 sexually experienced female adolescents who did not intend to become pregnant: 349 were pregnant for the first time, and 264 had never been pregnant. Mediation and moderation analyses were performed. An earlier AFSI was associated with unintended pregnancy 1–6 years after first sexual intercourse by increasing the adolescents' likelihood of having less education and being involved with partners older than themselves. There was no significant direct effect of AFSI on pregnancy occurrence after controlling for the mediators. Our findings bring to light nonsexual mechanisms that must be considered in public health interventions aimed at preventing unintended pregnancies among adolescents who engaged in sexual intercourse at early ages. Specific implications are discussed.