(710) Does Second-Trimester Abdominal Wall Defect Size Predict Neonatal Outcomes in Gastroschisis?

To determine whether abdominal wall defect size at 2nd trimester prenatal ultrasound predicts composite neonatal outcomes in fetuses with gastroschisis.

Study Design:
This IRB-approved retrospective cohort study included all pregnancies with a prenatal ultrasound diagnosis of gastroschisis at a tertiary center between January 2000 and December 2023. Cases were identified through the fetal imaging database, and abdominal wall defect size was measured in axial views using the umbilical cord insertion site as a landmark. We then applied a generalized additive model (GAM) to assess the association between abdominal wall defect size (measured at the second trimester ultrasound) and neonatal outcomes, adjusting for gestational age at delivery, external and intra-abdominal bowel dilation (EBD and IBD), abdominal circumference (AC), and fetal growth restriction (FGR).

Results:

N=71 pregnancies met inclusion criteria. The mean gestational age at the time of the reference ultrasound was 21.3 weeks (SD ±3.7). The model identified a “safe zone” between the 33rd and 55th percentiles of defect size (7.0–8.5 mm), where predicted neonatal outcomes were significantly better and the entire 85% confidence interval remained above zero. This middle range also represents the most reliable predictive zone, as model accuracy decreases at extremes. In adjusted analysis, IBD (β = 2.78, p = 0.002) and EBD (β = 2.15, p = 0.025) were independent predictors of worse outcomes.

Conclusion:

In this single-center, tertiary referral center study, mid-range abdominal wall defect sizes—between the 33rd and 55th percentiles—were associated with significantly improved composite neonatal outcomes, while external and intra-abdominal bowel dilation independently predicted worse outcomes. While it is well established that large defects are associated with extensive herniation and visceral injury, our study robustly estimates the thresholds for association of outcomes based on specific estimates of the size of the defect at the time of fetal anatomic survey. This should aid MFM clinicians in counseling patients reliably.