When is the optimal time to deliver late preterm IUGR fetuses with abnormal umbilical artery Dopplers?

Objective: To determine the optimal timing of delivery in late preterm intrauterine growth restriction (IUGR) fetuses with abnormal umbilical artery Doppler (UAD) indices.Methods: A decision-analytic model was built to determine the optimal gestational age (GA) of delivery in a theoretic cohort of 10 000 IUGR fetuses with elevated UAD systolic/diastolic ratios diagnosed at 34 weeks. All inputs were derived from the literature. Strategies involving expectant management accounted for the probabilities of stillbirth, spontaneous delivery and induction of labor for UAD absent or reversed end-diastolic flow (AREDF) at each successive week. Outcomes included short- and long-term neonatal morbidity and mortality with quality-adjusted life years (QALYs) generated based on these outcomes. Base case, sensitivity analyses and a Monte Carlo simulation were performed.Results: The optimal GA for delivery is 35 weeks, which minimized perinatal deaths and maximized total QALYs. Earlier delivery became optimal once the risk of stillbirth was threefold our baseline assumption; our model was also robust until the risk of AREDF at 35 weeks was half our baseline assumption, after which delivery at 36 weeks was preferred. Delivery at 35 weeks was the optimal strategy in 77% of trials in Monte Carlo multivariable sensitivity analysis.Conclusions: Weighing the risks of iatrogenic prematurity against the poor outcomes associated with AREDF, the ideal GA to deliver late preterm IUGR fetuses with elevated UAD indices is 35 weeks.