Fetal growth restriction (FGR) is a known cause of neonatal morbidity. Recent new guidelines changed the diagnostic criteria from estimated fetal weight (EFW) < 10%ile alone to EFW and/or abdominal circumference (AC) < 10%ile. Diagnosing and treating FGR is important to optimize fetal and neonatal outcomes, however does require increased antenatal surveillance. This study compares neonatal outcomes and resource utilization across 3 methods of FGR diagnosis.

This secondary analysis of a retrospective cohort study classified three groups of women who delivered at our institution based on timing of how we diagnosed FGR: Group 1 (7/1/2017-6/30/2018; EFW < 10%ile), Group 2 (4/1/2020-3/31/2021; EFW < 10%ile or EFW 10-19%ile and AC < 5%ile), and Group 3 (8/1/2021-7/31/2022; EFW and/or AC < 10%ile). Inclusion criteria were FGR diagnosis and dating ultrasound (US) prior to 22 weeks. Multifetal gestations and fetuses with major anomalies were excluded. The primary outcome was a composite of neonatal complications. Continuous outcome variables were compared across the three groups using ANOVA. Categorical outcomes variables were compared using X2. P-value < 0.05 was statistically significant.

320 pregnancies with FGR diagnosis were identified (n=44 Group 1, n=96 Group 2, n=180 Group 3). Overall, gestational age at delivery was similar between groups (Table 1). Compared to Group 1, numbers of growth US and BPP were higher in Group 2 and highest in Group 3. The neonatal complications composite rate was 56.8% in Group 1, 45.8% in Group 2, and 37.2% in Group 3 (p=0.046; Table 2). NICU admission rate was 54.6% in Group 1, 41.1% in Group 2, and 34.1% in Group 3 (p=0.04).

The newest method of FGR diagnosis resulted in the highest numbers of prenatal growth US and BPP. The composite complication rate for neonates with prenatal FGR diagnosis was lower during the time period using the new FGR criteria, however this may be due to the inclusion of neonates with less severe FGR and/or absence of SGA. Further investigation is needed into whether broader definitions of FGR result in improved neonatal outcomes.