Do Gestational Age Dating Criteria Matter in Medically Indicated Late Preterm, Early-Term, and Full-Term Inductions of Labor?

Objectives To assess short-term neonatal respiratory morbidity from inductions of labor (IOL) in well-dated (WD) pregnancies (dating ultrasound [US] <20 0/7 weeks) versus non-well-dated (NWD) pregnancies when applying National Institutes of Health/Society for Maternal-Fetal Medicine/American College of Obstetricians and Gynecologists delivery recommendations at >= 34 0/7 weeks. Methods Ours was a 1-year retrospective cohort of women with medically indicated IOL between 34 0/7 and 40 6/7 weeks with a live, cephalic, singleton gestation and no lethal anomaly. The primary outcome was a composite of neonatal respiratory morbidity (respiratory distress syndrome, transient tachypnea of the newborn, ventilator support, oxygen administration, and pneumonia). Results A total of 476 WD and 231 NWD women underwent IOL during the study period. The groups had similar maternal characteristics, indications for IOL, and mode of delivery. There was no difference in the rate of primary outcome (8.7% in NWD group vs 8.8% in WD group; P = 0.95). This finding persisted after control for parity, gestational age (GA) at first US, operator of the dating US, and exposure to antenatal corticosteroids and magnesium sulfate. When stratified by GA at delivery and GA at first US, these findings persisted even when the dating US was performed at >35 weeks. There were no differences in maternal or other neonatal outcomes between the WD and NWD pregnancies. Conclusions In our cohort of medically indicated IOL, a dating US before 20 weeks was not associated with a difference in neonatal respiratory morbidity.