Second-trimester fetal growth and the risk of poor obstetric and neonatal outcomes

Objective: To compare outcomes of fetuses with an estimated fetal weight (EFW) <25th percentile in the second trimester to those in fetuses with EFW ≥25^th percentile in the second trimester. Methods: We compared outcomes of 252 pregnancies with an EFW <25^th percentile at 18-24 weeks' gestation with those of 265 controls. All pregnancies had early dating by ultrasonography. We excluded fetuses with aneuploidy, major malformations, second-trimester rupture of membranes, and multiple pregnancies. Results: Second-trimester EFW <25^th percentile was significantly associated with higher rates of fetal or neonatal death, third-trimester small for gestational age (SGA), Doppler abnormalities, indicated preterm birth, gestational hypertension or pre-eclampsia before labor, lower birth weight, birth weight <10^th percentile, birth weight <5th percentile, and admission to the neonatal intensive care unit. Many of these associations remained even after excluding patients with oligohydramnios, fetal echogenic bowel, and growth asymmetry. Conclusion: Second-trimester SGA, as defined by an EFW <25^th percentile using current growth curves, is associated with poor obstetric and neonatal outcomes. Increased surveillance of such pregnancies may be necessary.