Stillbirth as a risk factor for subsequent infant mortality

BackgroundInfant mortality is an important indicator of the health and wellness of a society. Multiple risk factors for infant mortality have been identified and investigated; however, the influence of prior pregnancy experience on subsequent infant mortality is under-researched.AimsTo examine the association between stillbirth in the first pregnancy and risk for infant mortality in the second pregnancy in a large population-based dataset.Study designPopulation-based, retrospective cohort studySubjectsMissouri maternally linked cohort data files were utilized from 1989 through 2005. Analyses were restricted to women who had two singleton pregnancies during the study period.Outcome measuresThe exposure was stillbirth in the first pregnancy, while the primary outcome was infant mortality in the second pregnancy.ResultsWomen who experienced stillbirth in their first pregnancy were more likely to be of advanced age, black, and obese and had higher rates of pregnancy-related complications (p < 0.01). Previous stillbirth was associated with an elevated risk for subsequent infant mortality (AHR = 2.51, 95% CI: 1.73–3.65) and neonatal mortality (AHR = 3.04, 95% CI: 1.99–4.65), after adjustment for socio-demographic variables and pregnancy complications. Risk estimates for mortality in the second pregnancy were most profound among black mothers with a history of stillbirth in the first pregnancy [risk for infant mortality: (AHR = 2.68, 95% CI: 1.41–5.09) and neonatal death: (AHR = 4.25, 95% CI: 2.34–7.60)].ConclusionsWomen with prior stillbirth bear elevated risks for subsequent infant mortality. Women's previous childbearing experiences could serve as important criteria in determining appropriate interconception strategies to improve subsequent feto-infant health and survival.