Survival rates and mode of delivery for vertex preterm neonates according to small- or appropriate-for-gestational-age status.

OBJECTIVE: The goal was to characterize the relationship between cesarean section delivery and death for preterm vertex neonates according to intrauterine growth.
METHODS: Maternal and infant data from the National Center for Health Statistics for 1999 and 2000 were analyzed. Neonates with gestational ages of 26 to 36 weeks were characterized as small for gestational age (<10th percentile) or appropriate for gestational age (10th to 90th percentile). Mortality rates at 28 days and relative risks were calculated for each gestational age group according to mode of delivery.
RESULTS: Cesarean section rates were higher for small-for-gestational-age neonates compared with appropriate-for-gestational-age neonates, most prominently from 26 weeks to 32 weeks of gestation, at which small-for-gestational-age neonates had cesarean section rates of 50% to 67%, whereas appropriate-for-gestational-age neonates had rates of 22% to 38%. Small-for-gestational-age neonates at gestational ages of <31 weeks had increased survival rates associated with cesarean section, whereas small-for-gestational-age neonates at >33 weeks and appropriate-for-gestational-age neonates overall had decreased survival rates associated with cesarean section. After adjustment for sociodemographic and medical factors, the survival advantage for small-for-gestational-age neonates at gestational ages of 26 to 30 weeks persisted.
CONCLUSIONS: Cesarean section delivery was associated with survival for preterm small-for-gestational-age neonates but not preterm appropriate-for-gestational-age neonates. We speculate that vaginal delivery may be particularly stressful for small-for-gestational-age neonates. We found no evidence that prematurity alone is a valid indication for cesarean section for preterm appropriate-for-gestational-age neonates.