Small size for gestational age and the risk for infant mortality in the subsequent pregnancy

Abstract

Purpose: To examine the association between small for gestational age (SGA) in the first pregnancy and risk for infant mortality in the second pregnancy.

Methods: This is a population-based, retrospective cohort study in which we used the Missouri maternally linked cohort dataset for 1978-2005. Analyses were restricted to women who had two singleton pregnancies during the study period. The exposure was SGA in the first pregnancy, whereas the primary outcome was infant mortality in the second pregnancy. Kaplan-Meier Estimate and Cox proportional hazard regression were conducted.

Results: Infant mortality was significantly greater among mothers with previous SGA (P < .01). A persistent association of previous SGA with subsequent infant mortality was observed (adjusted hazard ratio [AHR] 1.35, 95% confidence interval [95% CI] 1.24-1.48). Race-specific data illustrated that black women with a previous SGA birth were 40% more likely to experience infant mortality (AHR 1.40, 95% CI 1.21-1.63) than their counterparts without a history of SGA, but white women with a previous SGA had an increased risk of 31% (AHR 1.31, 95% CI 1.17-1.46).

Conclusions: Women with previous SGA bear increased risks for subsequent infant mortality, which was greater among black mothers. Hence, SGA plays an important role in the black-white disparity in infant mortality. Women's previous childbearing experiences could serve as important criterion in determining appropriate interconception strategies to improve infant health and survival.

Fig. 1

Flow diagram of exclusion criteria for the study.

Fig. 2

Infant mortality rates among the study population at second pregnancy (Missouri: 1978–2005).

Fig. 3

Kaplan-Meier curves comparing cumulative probability of infant death between infants born to mothers who had previous SGA and with those born to mothers with no previous SGA (Missouri: 1978–2005).