Is Small for Gestational Age a Marker of Future Fetal Survival In Utero?

OBJECTIVE: We sought to assess whether small for gestational age is a risk factor for stillbirth of a subsequent sibling. METHODS: The Missouri maternally linked cohort data set, containing data on births from 1978 through 1997, was used. We identified the study group (women who delivered a SGA infant in the first pregnancy) and a comparison group (women who delivered a non-SGA infant in their first pregnancy) and compared the outcome (stillbirth) in the second pregnancy between both groups. RESULTS: We analyzed information on the first and second pregnancies of 402,015 women (43,549 [10.8%] in the study arm and 358,466 [89.2%] in the comparison arm). Of the 1,883 cases of stillbirth in the second pregnancy, 314 cases occurred in mothers with a history of SGA (stillbirth rate 7.2/1,000) and 1,569 in the comparison group (stillbirth rate 4.4/1,000), P < .001. The adjusted risk of stillbirth was 60% higher in women with a prior SGA (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.4–1.8). The risk for stillbirth in the second pregnancy increased with decreasing gestational age at birth of the SGA infant in the first pregnancy (term: OR 1.4, 95% CI 1.2–1.6; preterm: OR 2.8, 95% CI 2.0–3.8; and very preterm: OR 4.2, 95% CI 2.4–7.3), P for trend < .001. CONCLUSION: Small for gestational age is a marker for subsequent stillbirth, and the risk rises with decreasing gestational age of the SGA birth. This information is potentially useful for counseling parents of SGA infants. LEVEL OF EVIDENCE: II-2