(480) Comparing adverse outcomes of FGR defined by abdominal circumference versus EFW: A Retrospective Chart Review

Objective:
To compare adverse perinatal outcomes in pregnancies diagnosed with fetal growth restriction (FGR) based on isolated abdominal circumference (AC) versus estimated fetal weight (EFW) < 10th percentile.
Limited literature exists on the clinical significance and outcomes of AC-defined FGR, resulting in variability in practice, particularly regarding surveillance intensity and timing of delivery. This study aims to evaluate our institution’s experience to inform decision-making for pregnancies affected by AC-defined FGR.

Study Design:
This was a retrospective chart review of all singleton gestations who underwent growth ultrasounds and delivered at a single health system from 07/02/2021-06/30/2024. The study group comprised of patients with AC < 10th percentile and EFW ≥ 10th percentile. The control group comprised of patients with overall EFW < 10th percentile. Data was extracted from electronic medical records. Outcomes evaluated included gestational age at diagnosis and delivery, mode of delivery, maternal and neonatal outcomes. A subgroup analysis was done on perinatal outcomes at delivery by gestational week in the AC group. Data was analyzed using independent T test and Chi-square tests with significance defined at p < 0.05.

Results:
Of 277 pregnancies, 99 were in the AC group and 178 in the EFW group. The AC group had later gestational age at diagnosis (33.6 vs 31.8 weeks) and delivery (38.2 vs 36.5 weeks). Compared to the EFW group, the AC group had lower rates of preterm delivery (15.2% vs 28.7%), NICU admission (22.2% vs 40.4%), and SGA (60.6% vs 80.9%). Gestational hypertension was more common in the AC group, while preeclampsia was more frequent in the EFW group. In the AC group, an increase in SGA and NICU admissions was observed at 37 weeks compared to other gestational weeks at term.

Conclusion:
Our findings suggest that isolated AC-defined FGR is associated with better neonatal outcomes than EFW-defined FGR, indicating that these two phenotypes may warrant different clinical approaches. Further prospective studies are needed to guide optimal timing of delivery for AC-defined FGR.