Defining fetal growth restriction: abdominal circumference as an alternative criterion

Area of Science:

• Maternal-fetal medicine
• Diagnostic imaging in obstetrics
• Fetal growth assessment

Background:

• Fetal growth restriction (FGR) affects fetal development and birth outcomes.
• Accurate screening for small for gestational age (SGA) is crucial for timely intervention.
• Current screening methods using estimated fetal weight (EFW) have limitations in sensitivity.

Purpose of the Study:

• To evaluate the effectiveness of using abdominal circumference percentile (AC) for defining FGR.
• To determine if AC improves ultrasound screening for SGA at ≥36 weeks gestation.
• To compare the diagnostic performance of AC versus EFW in identifying SGA.

Main Methods:

• Retrospective analysis of 1594 ultrasounds in non-anomalous singletons at ≥36 weeks.
• FGR defined by EFW <10th percentile and/or AC <10th percentile for gestational age.
• Calculation of sensitivity, specificity, false-positive rate (FPR), positive-predictive value (PPV), and AUC for screening criteria.

Main Results:

• Using AC <10 demonstrated higher sensitivity (64.0%) and a similar PPV (81.3%) compared to EFW <10 (50.6% sensitivity, 83.8% PPV).
• The combined criterion of AC or EFW <10 yielded the highest AUC (0.821), indicating superior overall screening performance.
• These findings remained consistent across different maternal race/ethnicity and BMI strata.

Conclusions:

• Abdominal circumference percentile (AC <10) is a more sensitive screening criterion for SGA than EFW <10.
• The combined use of AC or EFW <10 offers an optimal balance of sensitivity and specificity with a low FPR.
• AC <10 is a viable alternative to EFW for diagnosing FGR, improving SGA screening in late pregnancy.