Infant mortality and subsequent risk of stillbirth

Background: Despite the comparatively high prevalence of stillbirth and infant mortality in the US, little is known regarding the association between the two. Previous research has indicated that women with prior fetal loss are at higher risk for adverse outcomes in subsequent pregnancies, including low birth weight, preterm, and stillbirth. However, the linkage between prior infant mortality and subsequent stillbirth is relatively under-studied. Methods: We utilized data from the Missouri maternally linked cohort data files for 1989-2005 to examine the association between infant mortality (exposure) and subsequent stillbirth (primary outcome). We employed odds ratios generated from multi-variable logistic models to approximate relative risks. Results: Women who experienced infant death during their first pregnancy were more likely to be black and unmarried with less than a high school education (p<0.01). They also had higher rates of pregnancy-related complications (p<0.01), including chronic hypertension (p=0.02), pre-eclampsia (p=0.01), and abruptio placenta (p<0.01). After controlling for the aforementioned risk factors, previous infant mortality was still associated with a three-fold elevated risk of subsequent stillbirth (AOR=3.19, 95% CI 1.98-5.14). For white women, the likelihood of stillbirth was more than twice as great (AOR=2.19, 95% CI 1.08-4.44), whereas black women had a five-fold increased risk (AOR=5.24, 95% CI 2.71-10.14). Conclusions: Women with a history of infant mortality experience higher risk for subsequent stillbirth, with the most profound elevated risk observed among black women. Interconception care strategy that addresses previous childbearing experiences of women is urgently needed to avert subsequent fetal loss, especially among black women.