Risk factors for teenage pregnancy are linked to many factors, including a family history of teenage pregnancy. This research examines whether a mother’s teenage childbearing or an older sister’s teenage pregnancy more strongly predicts teenage pregnancy in a younger sister.
This study used linkable administrative databases housed at the Manitoba Centre for Health Policy (MCHP). The original cohort consisted of 17,115 women born in Manitoba between April 1, 1979 and March 31, 1994, who stayed in the province until at least their 20th birthday, had at least one older sister, and had no missing values on key variables. Propensity score matching (1:2) was used to create balanced cohorts for two logistic regression models; one examining the impact of an older sister’s teenage pregnancy on a younger sister's teenage pregnancy and the other analyzing the effect of the mother’s teenage childbearing on a younger sister's teenage pregnancy odds.
The adjusted odds of becoming pregnant between ages 14 and 19 for teens with at least one older sister having a teenage pregnancy were 3.06 (99% CI 2.53 - 3.64) times higher than for women whose older sister(s) did not have a teenage pregnancy. Teenage daughters of mothers who had their first child before age 20 had 1.51 (99% CI 1.29 - 1.78) times higher odds of pregnancy than those whose mothers had their first child after age 19. Educational achievement was adjusted for in a sub-population examining the odds of pregnancy between ages 16 and 19. After this adjustment, the odds of teenage pregnancy for teens with at least one older sister who had a teenage pregnancy were reduced to 2.34 (99% CI 1.92-2.86) and the odds of pregnancy for teen daughters of teenage mothers were reduced to 1.35 (99% CI 1.15-1.59).
Given that an older sister’s teenage pregnancy has a much stronger impact than a mother’s teenage pregnancy, this study suggests social modeling to be a stronger risk factor for teenage pregnancy than living in an adverse environment created by a mother's adolescent childbearing. This study contributes to understanding of the broader topic “who is influential about what” within the family.