The contribution of elective delivery to severe respiratory distress at term

Abstract

Objective: To determine the incidence of respiratory distress syndrome (RDS) requiring mechanical ventilation (MV) at 37, 38, 39, and 40 weeks of gestation and to determine whether elective delivery without documented fetal lung maturity accounts for a significant proportion of RDS requiring MV at 37–38 weeks of gestation. Methods: We identified all inborn neonates with RDS requiring MV delivered at 37 0/7–40 6/7 weeks of gestation from January 1, 1990 to December 31, 1999. Cases were excluded for sepsis, pneumonia, meconium aspiration, asphyxia, pulmonary hemorrhage, hydrops, chromosomal abnormality, or congenital malformations affecting respiration. Charts were reviewed to confirm gestational age, delivery reason (elective, spontaneous, or indicated), and the diagnosis of RDS: tachypnea, retractions, grunting, oxygen and ventilator requirement, chest X-ray indicating diffuse haziness, air bronchograms, granularity, and small lung volumes. Secondary neonatal outcomes included pulmonary air leak or severe pulmonary hypertension (ECMO or inhaled nitric oxide). Results: 35,031 deliveries occurred from 37 0/7–40 6/7 weeks of gestation, of which 18 (0.05%) were identified with RDS requiring MV. Nine infants were delivered at 37 0/7–37 6/7 weeks of gestation, mean 37.4 + 0.2 weeks (OR= 38.5; 95% CI= 8.3, 178.3); seven were delivered at 38 0/7–38 6/7 weeks of gestation, mean 38.4 + 0.2 weeks (OR= 13.3; 95% CI= 2.8, 64.0); and two were delivered at 39 0/7–40 6/7 weeks of gestation, mean 39.3 + 0.2 weeks (reference). Six of 18 infants were electively delivered without a mature lung profile. Secondary adverse neonatal outcomes occurred with similar frequency by gestational age. Conclusions: Infants born at 37 0/7–38 6/7 weeks of gestation experience RDS requiring MV significantly more often than infants delivered at 39 0/7–40 6/7 weeks of gestation. Six of 18 RDS cases (33%) may have been prevented by avoiding elective delivery before 39 weeks of gestation in the absence of documented fetal lung maturity.