Neonatal Outcomes of Infants Diagnosed with Fetal Growth Restriction during Late Pregnancy versus after Birth

Objective: The aim of this study was to investigate the potential differences in the outcomes of neonates in whom FGR was diagnosed late in pregnancy as compared to those in whom growth restriction was diagnosed after birth. Methods: A retrospective study was conducted in a tertiary medical center between 2017 and 2019. The study included women carrying a single infant with an estimated fetal weight below the tenth percentile in whom FGR was diagnosed during late pregnancy, after 32 gestational weeks (known late-onset FGR; study group) or only after birth (unknown FGR; control group). Data were collected by review of the electronic health records. The primary outcome measure was the rate of composite adverse neonatal outcome. Results: A total of 328 women were included, 77 (23.47%) in the known-FGR group and 251 (75.53%) in the unknown-FGR group. In the known-FGR group, an etiology for the FGR was identified in 28.57% cases, most commonly placental insufficiency (21.74%). Compared to the unknown-FGR group, the known-FGR group was characterized by significantly higher rates of elective cesarean delivery (15.58% vs. 9.96%, p < 0.001), preterm birth (18.18% vs. 3.98%, p < 0.01), and labor induction (67.53% vs. 21.51%, p < 0.01). A significantly higher proportion of neonates in the known-FGR group had a positive composite adverse outcome (38.96% vs. 15.53%, p < 0.01). For multivariate regression analysis adjusted for maternal age, gestational age at delivery, and mode of delivery, there was no difference between groups in the primary outcome (aOR 1.73, CI 0.89-3.35, p = 0.1). Every additional gestational week at delivery was a protective factor (aOR = 0.7, 95% CI 0.56-0.86, p < 0.01). Conclusions: A prenatal diagnosis of late-onset FGR is associated with higher intervention and preterm birth rates as compared to a diagnosis made after birth. Fetuses diagnosed with late-onset FGR during pregnancy should undergo specific and personalized assessment to determine the cause and severity of the growth delay and the best management strategy. This study highlights the importance of careful decision-making regarding the induction of labor in late-onset FGR.