Effect of the New Diagnostic Criteria of Fetal Growth Restriction on Obstetric and Neonatal Outcomes

INTRODUCTION: The diagnostic criteria of fetal growth restriction (FGR) was modified by the Society of Maternal-Fetal Medicine in 2020 to include both an abdominal circumference (AC) and estimated fetal weight (EFW) less than the 10th percentile as opposed to previous definition using only the EFW. We sought to evaluate the outcomes of this criteria modification. METHODS: This retrospective study compared the incidence, obstetrical and neonatal outcomes before (group 1, 2020) and after (group 2, 2021) the implementation of the modified diagnostic criteria at a single institution. This is an IRB-approved study. RESULTS: Of the 459 pregnancies with FGR included in this study, 100 were diagnosed in 2020 (group 1) and 359, in 2021 (group 2). An increase in the incidence of FGR was noted after the modification, 1.5% versus 5.3% ( P <.05). Median gestational age (weeks) at delivery decreased from 38.1 (Q1, 37.1; Q3, 39.1) in 2020 to 37.4 (Q1, 36.1; Q3, 38.3) in 2021 ( P <.05). There were no statistically significant differences in obstetrical outcomes. An increase in the frequency of respiratory distress syndrome was observed, 6 (6%) versus 51 (14.2%), P <.05, and median length of neonatal stay 2.0 (Q1, 1.0; Q3, 3.0) and 2.0 (Q1, 2.0; Q3, 12.0) in group 1 compared to group 2 ( P <.05). CONCLUSION: The new diagnostic criteria for FGR is associated with increased incidence of diagnosis, neonatal respiratory distress, longer neonatal hospital admissions, and lower gestational age of delivery with no difference in obstetrical outcomes. It remains uncertain whether this modification will translate to improved outcomes, and larger multicenter prospective studies are needed.