All-cause infant mortality and the risk for subsequent preterm birth.

Aim: The aim of this paper was to assess the association between all-cause infant mortality (death<365 days) in the first pregnancy and the risk of preterm birth (<37 weeks of gestation) in the second pregnancy.

Methods: Using the Missouri maternally linked dataset from 1989 to 2005 (N.=639134 singleton live births), we conducted a population-based retrospective cohort analysis with women who had two singleton births between 1989 and 2005. We employed Cox Proportional Hazards Regression to generate adjusted hazard ratios (AHR) and 95% confidence intervals (CI) to approximate relative risks.

Results: Prior infant mortality was associated with an increased risk for preterm birth in the second pregnancy (AHR=1.96, 95% CI=1.80-2.13). For black women, the risk of preterm birth following infant mortality was more than three-fold (AHR=3.37, 95% CI=2.92-3.89), while the risk for white women was twice as high (AHR=2.04, 95% CI=1.86-2.26) (referent=white women without infant death in the first pregnancy).

Conclusion: Women with a history of infant mortality are at risk for preterm birth in subsequent pregnancies. This risk was significantly elevated for black women. These findings provide further evidence that previous childbearing experiences play a critical role in the occurrence of adverse feto-infant outcomes.