LAUSR

Objectives: Female family members affect both the likelihood of adolescent pregnancy and the outcome of that pregnancy. We examined the degree to which an older sister’s adolescent reproductive outcomes affect her younger sister’s reproductive behavior, and whether relationships in adolescent pregnancy among sisters born to adolescent mothers differ from those born to nonadolescent mothers. Methods: We followed a birth cohort in Manitoba, Ontario, Canada, to age 20 using linkable administrative databases housed at the Manitoba Centre for Health Policy. The cohort consisted of 12 391 girls born in Manitoba between April 1, 1984, and March 31, 1996, who had 1 older sister. We used logistic regression models to examine the relationships among familial adolescent pregnancy outcomes. Results: Compared with adolescent girls whose older sister did not have an adolescent pregnancy, adolescent girls whose older sister had an adolescent pregnancy were more likely to have a pregnancy (adjusted odds ratio [aOR] = 2.57), regardless of whether that pregnancy was completed (aOR = 2.56) or terminated (aOR = 2.59). Relationships in adolescent pregnancy among sisters were much stronger for those born to nonadolescent mothers (aOR = 3.16 [older sister completed adolescent pregnancy] and 3.18 [older sister terminated adolescent pregnancy]) than to adolescent mothers (aOR = 1.65 [older sister completed adolescent pregnancy] and 1.77 [older sister terminated adolescent pregnancy]). For younger sisters having an adolescent pregnancy, the odds of her completing the pregnancy were reduced if her older sister had terminated an adolescent pregnancy and her mother had not been an adolescent mother (aOR = 0.38). Conclusions: Younger sisters of adolescents who had a pregnancy may benefit from targeted interventions to reduce their likelihood of adolescent pregnancies.