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Ultrasound/Imaging

Poster Session 4

(1188) Sonographic versus birth weight for fetal growth curves in twins

Wednesday, February 14, 2024
1:00 PM – 2:30 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective: Twin gestations are subjected to higher rates of growth abnormalities. Accurate locally customized reference values may contribute to accurately diagnosing abnormal fetal growth. We aimed to determine reference values for ultrasound-based estimated fetal weight (EFW) and compared them to the actual birth-weight curve for twins.

Study Design: A multicenter retrospective longitudinal analysis of sonographically EFW evaluations of twin gestations performed between 2009 and 2022 in 10 medical centers in Israel. Estimated fetal weight at 14-40 gestational weeks was calculated using the Hadlock 1985 formula. No exclusions were made on grounds of chorionicity. The non-parametric Quantile Generalized Additive Model (QGAM) approach was employed. Following the calculation of the 10th, 50th, and 90th percentile for each gestational week and the construction of ultrasound-based curves, we compared the 10th percentile at 22 to 37 gestational weeks with that calculated using the Israeli local  twin specific actual birth weight curve.



Results: After cleaning procedures, the dataset comprised data from 5,506 mothers with approximately 26,500 sonographic evaluations of  EFW (median 5 evaluations per pregnancy). Values corresponding to the 50th, 10th, and 90th percentiles were calculated with the construction of the ultrasound-based reference curve. The 10th percentile of the sonographic EFW curve was about 100-200 grams higher than the 10th percentile of the birth-weight curve, matching the 15-20 growth percentiles (figure). 

Conclusion: The sonographic EFW curve and the actual birth-weight curve established different cutoff values for the 10th percentile in twin gestation. Choosing the appropriate growth curve is important to avoid misdiagnosis of growth abnormalities.