Infant mortality and subsequent risk of stillbirth: a retrospective cohort study.

OBJECTIVE

To examine the association between infant mortality in a first pregnancy and risk for stillbirth in a second pregnancy.

DESIGN

Population-based, retrospective cohort study.

SETTING

Maternally linked cohort data files for the state of Missouri.

POPULATION

Women who had two singleton pregnancies in Missouri during the period 1989-2005 (n = 320 350).

METHODS

Women whose first pregnancy resulted in infant death were compared with those whose infant from the first pregnancy survived the first year of life. The Kaplan-Meier product limit estimator was employed to compare probabilities for stillbirth in the second pregnancy between both groups of women. Adjusted hazard ratios (AHRs) and 95% confidence intervals (95% CIs) were generated to assess the association between infant mortality in the first pregnancy and stillbirth in the second pregnancy.

MAIN OUTCOME MEASURES

Exposure was defined as infant mortality in the first pregnancy, and the outcome was defined as stillbirth in the second pregnancy.

RESULTS

Women with prior infant deaths were about three times as likely to experience stillbirth in their subsequent pregnancy (AHR 2.91; 95% CI 2.02-4.18). White women with a previous infant death were nearly twice as likely to experience a subsequent stillbirth, compared with white women with a surviving infant (AHR 1.96; 95% CI 1.13-3.39). Black women with a previous infant death were more than four times as likely to experience subsequent stillbirth, compared with black women with a surviving infant (AHR 4.28; 95% CI 2.61-6.99).

CONCLUSIONS

Previous infant mortality results in an elevated risk for subsequent stillbirth, with the most profound increase observed among black women. Interconception care should consider prior childbearing experiences to avert subsequent fetal loss.