Second births to teenage mothers: risk factors for low birth weight and preterm birth.

CONTEXT: Teenagers are more likely than older women to have a low-birth-weight infant or a preterm birth, and the risks may be particularly high when they have a second birth. Identifying predictors of these outcomes in second teenage births is essential for developing preventive strategies.
METHODS: Birth certificate data for 1993-2002 were linked to identify second births to Milwaukee teenagers. Predictors of having a low-birth-weight second infant or a preterm second birth were identified using logistic regression.
RESULTS: The same proportion of first and second infants were low-birth-weight (12%), but second births were more likely than first births to be preterm (15% vs. 12%). In analyses that adjusted for demographic, pregnancy and behavioral characteristics, the odds that a second infant was low-birth-weight or preterm were elevated if the mother smoked during pregnancy (odds ratios, 2.2 and 1.9, respectively), had inadequate prenatal weight gain (1.8 and 1.4), had an interpregnancy interval of less than 18 months (1.6-2.9 and 1.4-2.3) or was black (2.7 and 1.7). Women who had received an adequate level of prenatal care had reduced odds of both outcomes (0.6 and 0.4). Women younger than 16 also had increased odds of having a low-birth-weight second infant. Further adjustment for socioeconomic characteristics yielded largely the same results. In addition, women who were unmarried or did not identify a father were at increased risk of both outcomes (1.5 for each), and poor women were at risk of having a low-birth-weight infant (1.3).
CONCLUSIONS: Predictors of poor birth outcomes include modifiable behaviors. Prenatal interventions addressing these behaviors could help improve outcomes.