The effects of labor on infant mortality among small-for-gestational-age infants in the USA

To determine whether the presence of labor affects infant mortality among small-for-gestational-age (SGA) infants.

Data were derived from the United States national linked birth/infant death data sets for 1995-97. Singleton SGA live births in cephalic presentation delivered at 24-42 weeks' gestation were included. Mortality rates for SGA infants exposed and unexposed to labor were compared, and relative risks (RR) were derived using multivariable logistic regression models, after adjusting for potential confounding factors.

Of 986 405 SGA infants, 87.4% were exposed to labor. Infants exposed to labor at 24-31 weeks had greater risks of dying during the early neonatal period (RR 1.79-1.86). Decreased risks of late and postneonatal death were observed at all gestational ages in the presence of labor.

Exposure to labor is associated with an increased risk of early neonatal death among SGA infants, especially at gestational ages below 32 weeks. Future randomized trials are warranted to determine the optimal obstetric management of these high-risk infants.