Increased risks of neonatal and postneonatal mortality associated with teenage pregnancy had different explanations

To determine the potential pathway of the association between teenage pregnancy and neonatal and postneonatal mortality.

We carried out a retrospective cohort study of 4,037,009 nulliparous pregnant women under 25 years old who had a live singleton birth during 1995 to 2000, based on linked birth and infant death data set of the United States.

Teenage pregnancy (10-19 years old) was associated with increased neonatal mortality (odds ratio [OR]: 1.20, 95% confidence interval [CI]=1.16-1.24) and postneonatal mortality (OR: 1.47, 95% CI=1.41-1.54) after adjustment for potential confounders. With further adjustment for weight gain during pregnancy, teenage pregnancy was still associated with increased risk of neonatal (OR: 1.23, 95% CI=1.19-1.28) and postneonatal mortality (OR: 1.48, 95% CI=1.42-1.55). When adjustment was made for gestational age at birth, there was no association of teenage pregnancy with neonatal mortality (OR: 0.98, 95% CI=0.95-1.02), whereas there was significant association with postneonatal mortality (OR: 1.40, 95% CI=1.34-1.46).

The increased risk of neonatal death associated with teenage pregnancy is largely attributable to higher risk of preterm births, whereas increased postneonatal mortality is independent of the known confounders and gestational age at birth.