The risk of neonatal respiratory morbidity according to the etiology of late preterm delivery.

Abstract

The risk of neonatal respiratory morbidity between indicated deliveries vs. spontaneous deliveries has not been consistent in previous studies, in spite of the traditional belief that chronic intrauterine stress might have protective effect on fetal lung maturation. We hypothesized that the heterogeneous etiology of indicated preterm delivery may obscure the relationship between the etiologies of preterm birth and neonatal respiratory morbidity. To address this issue, we divided the indicated preterm birth (PTB) into medically-indicated (without fetal compromise) PTB and maternal/fetal-indicated PTB, and compared the neonatal respiratory morbidity according to the etiology of late PTB. Neonatal respiratory morbidities were examined in neonates who were delivered between 34+0 and 36+6 weeks of gestation according to the etiology of PTB: 1) medically-indicated PTB (but without fetal compromise), 2) maternal/fetal-indicated PTB, or 3) spontaneous PTB such as preterm labor or preterm premature rupture of membranes. A total of 710 late preterm neonates were included in the study population, including 31 cases of medically-indicated PTB, 202 cases of maternal/fetal-indicated PTB, and 477 cases of spontaneous PTB. The rate of composite respiratory morbidity in cases of medically-indicated PTB is higher than both maternal/fetal-indicated PTB and spontaneous PTB (19% in medically-indicated PTB, 6% in maternal/fetal-indicated PTB, and 7% in spontaneous PTB). This difference between medically-indicated PTB and maternal/fetal-indicated PTB remained significant after adjustment for confounding variables. The medically-indicated PTB is associated with highest risk of neonatal respiratory morbidity in late PTB.