Neonatal outcomes after demonstrated fetal lung maturity before 39 weeks of gestation.

OBJECTIVE To compare outcomes among neonates delivered after documentation of fetal lung maturity before 39 weeks and those delivered at 39 or 40 weeks. METHODS This was a retrospective cohort study of women with singleton pregnancy delivered at 36 0/7 to 38 6/7 weeks after positive fetal lung maturity testing (based on amniotic fluid lecithin to sphingomyelin ratio) or at 39 0/7 to 40 6/7 weeks (without maturity testing) at our center from 1999 to 2008. Women with fetuses with major congenital anomalies, cord prolapse, nonreassuring antepartum testing, placental abruption, or oligohydramnios were excluded. A primary composite neonatal outcome included death, adverse respiratory outcomes, hypoglycemia, treated hyperbilirubinemia, generalized seizures, necrotizing enterocolitis, hypoxic ischemic encephalopathy, periventricular leukomalacia, and suspected or proven sepsis. RESULTS There were 459 neonates delivered at 36 to 38 weeks and 13,339 delivered at 39 to 40 weeks; mean birth weight was 3,107±548 g and 3,362±439 g, respectively. The risk of the composite adverse neonatal outcome was 6.1% for the 36- to 38-week group compared with 2.5% for the 39- to 40-week group (relative risk 2.4; confidence interval [CI] 1.7-3.5). After multivariable adjustment, early delivery remained significantly associated with an increased risk of the composite outcome (adjusted odds ratio [OR]1.7; CI 1.1-2.6) as well as several individual outcomes, including respiratory distress syndrome (adjusted OR 7.6; CI 2.2-26.6), treated hyperbilirubinemia (adjusted OR 11.2; CI 3.6-34), and hypoglycemia (adjusted OR 5.8; CI 2.4-14.3). CONCLUSION Neonates delivered at 36 to 38 weeks after confirmed fetal lung maturity are at higher risk of adverse outcomes than those delivered at 39 to 40 weeks.