Neonatal Outcomes in Spontaneous Versus Obstetrically Indicated Late Preterm Births in a Nova Scotia Population

Objective: To examine the indications for late preterm delivery in Nova Scotia and to compare the short-term outcomes by type of labour (spontaneous, induced, none). Methods: We conducted a population-based retrospective cohort study of late preterm births (34+0 to 36+6 weeks' gestation) between 1988 and 2009 using the Nova Scotia Atlee Perinatal Database. The association between labour type and neonatal outcomes was examined with logistic regression to estimate odds ratios with 95% confidence intervals. Results: Of the 10 315 late preterm births, 6228 followed spontaneous labour, 2338 followed induction of labour, and 1689 followed Caesarean section with no labour. Babies born following induction were at higher risk of developing hyperbilirubinemia (OR 1.14; 95% CI 1.03 to 1.27) and needing total parenteral nutrition (OR 1.52; 95% CI 1.15 to 1.99) than those born spontaneously. Those born without labour were at higher risk of needing resuscitation (OR 2.43; 95% CI 1.84 to 3.21) and total parenteral nutrition (OR 2.54; 95% CI 1.93 to 3.33) and developing transient tachypnea of the newborn (OR 1.43; 95% CI 1.10 to 1.85), hypoglycemia (OR 1.97; 95% CI 1.63 to 2.39), respiratory distress syndrome (OR 2.33; 95% CI 1.89 to 2.88), necrotizing enterocolitis (OR 3.20; 95% CI 1.07 to 9.53), and apneic spells (OR 1.29; 95% CI 1.05 to 1.59). When adjusted for maternal and fetal factors, odd ratios were only slightly attenuated. Conclusion: Among late preterm babies, those born by Caesarean section without labour are at increased risk of many adverse outcomes, while those born following induction of labour are at increased risk of few of the outcomes studied. Maternal and fetal factors other than those for which adjustment was made may contribute to the differences in outcome by labour type.