Delivery indication matters for perinatal outcomes in late preterm newborns.

Background: The late preterm (LP) rate in Western countries is 3-6% of all births, accounting for about two-thirds of the entire preterm population. However, all LP babies are not the same.

Aims: To identify pregnancies at risk for adverse outcomes in the LP period, we investigated how gestational age (GA) at delivery, delivery indication and prenatal risk factors may affect neonatal outcomes.

Study Design: Prospective cohort study among singleton infants born between 34 + 0 and 36 + 6 weeks, in Emilia Romagna, Italy, during 2013-2015.

Outcomes Measures: The primary outcome was a composite of adverse perinatal outcomes. Multivariate logistic regression models were used to, respectively, investigate the effects of GA at delivery, circumstances at parturition and prenatal risk factors, on study outcomes after controlling for confounding variable.

Results: Among 1867 births, 302, 504, and 1061 infants were born at 34, 35, and 36 weeks, respectively. There were no neonatal deaths. An increased risk of composite neonatal outcome was observed among 34 and 35 weeks deliveries compared with 36 weeks, and among indicated deliveries compared with spontaneous. When studying prenatal risk factors, neonatal morbidity was associated with pre gestational diabetes, preterm premature rupture of membranes (pPROM), maternal obesity, bleeding and polyhydramnios; instead, preeclampsia had a protective effect.

Conclusion: LP with indicated deliveries at 34 or 35 weeks, or with specific prenatal risk factors have worse neonatal outcome when compared to 36. Such differences should be considered when counseling patients and planning interventions such as timing of delivery in LP period.