Background: To examine the associations between adolescent pregnancy and pregnancy outcomes on substance use and suicide attempts in a sample who is at greater risk for substance use and suicide attempts -- those who have been involved with the juvenile justice and child welfare systems. Methods: Using a prospective, longitudinal design, we examined the role of adolescent pregnancy outcomes on risk for suicide attempts and substance use among a sample of 166 female adolescents with juvenile justice system and child welfare involvement. Results: Of participants, 36% (n = 60) reported at least one adolescent pregnancy with a total of 109 pregnancies reported. Adolescent pregnancy was associated with an increase in later suicide attempts (aOR = 1.68, 95% CI 1.06-2.72). Miscarriage was associated with a 2-fold increase in the likelihood of later suicide attempts, (aOR = 2.12, 95% CI 1.10-4.12). No participants who reported induced abortion (n = 13) reported suicide attempts. Adolescent pregnancy, miscarriage, and abortion were not significantly associated with later substance use (Ps > 0.05). Conclusions: Healthcare professionals should conduct routine screening for suicidality in the months following a miscarriage, offer education to caregivers about how to support youth who experience pregnancy loss, provide additional social supports and familiarize themselves with local and virtual behavioral health resources to prevent suicide attempts among female adolescents who are at high risk and experience miscarriage.