Preterm birth after mature fetal lung indices: is there any neonatal morbidity?

To determine the frequency of immediate morbidities in neonates with evidence of mature fetal lung indices who delivered before 37 weeks gestation.

A retrospective analysis was performed on pregnancies resulting in birth at < 37 weeks after mature fetal lung was documented by phosphatidylglycerol, lecithin/sphingomyelin ratio, or TDx-FLM studies. Pregnancies with multifetal gestations, maternal diabetes, or fetal anomalies were excluded.

179 patients were included. Eighty-one (45.3%) neonates did not sustain any morbidity, and 98 (54.7%) neonates sustained one or more morbidities. Compared to neonate without any morbidity, neonates experiencing morbidities were delivered at significantly younger gestation (35.7 ± 1.1 vs. 34.9 ± 1.5 weeks, respectively, p < 0.001) had lower birth- weight (2632.2 ± 475.5 vs. 2395.3 ± 496 g, respectively, p < 0.001), and required longer hospital stay (3.7 ± 2.8 vs. 6.9 ± 7.5 days, p < 0.001). A multivariate regression model was performed to control for the effect of birth-weight, steroid administration, and preterm premature rupture of membrane. An earlier gestational age at delivery was associated with a higher risk of neonatal morbidity. The risk of neonatal morbidity decreased by 40% (OR = 0.60, 95% CI = 0.41-0.88; p = 0.009) for each 1 week increase in gestational age.

Even in the presence of documented fetal lung maturity, major morbidities--including respiratory distress - may still occur.