[Chances of vaginal delivery with induction in severe preterm SGA fetus: An observational study]

Abstract

Objective: If a small for gestational age (SGA) foetus needs to be delivered because of severity (<3rd centile) attempting induction of labor theoretically increases the risk of caesarean section and neonatal acidosis, but these risks are poorly understood. This article aims to assess the risk of caesarean section and neonatal acidosis in attempted vaginal birth of a moderately preterm foetus in the setting of severe SGA.

Method: A single-centre hospital-based observational study conducted over a period of 17 consecutive years in mothers with a single foetus in cephalic presentation with severe SGA (<3rd centile) needing foetal extraction. Neonatal acidosis was considered moderate if pH<7.10 and severe if pH<7.0. The degree of severity of SGA was estimated according to the birth weight ratio.

Results: Four hundred and thirty-four foetuses with severe SGA were included during the period, 140 of whom were born after induction (32.3%). In this group, 66.4% of women achieved a vaginal birth (66.4%; 95% CI [58.0-74.2]) and the risk of moderate or severe acidosis was doubled compared with the group of foetuses who had undergone a planned caesarean section (7.9% vs. 3.1%, OR=2.7 [1.1-6.7]). Neither gestational age nor the degree of growth restriction was significantly related to the risk of caesarean section or to the risk of moderate or severe neonatal acidosis.

Conclusion: In cases of severe SGA before 37weeks' gestation, induction of labour allows vaginal delivery in two-thirds of cases. It is accompanied by a doubling of the risk of moderate or severe neonatal acidosis.

Keywords: Acidose néonatale; Déclenchement du travail; Induction of labor; Neonatal acidosis; PAG; Preterm birth; Prématurité; SGA; Tentative de voie basse; Trial of labor.