A prospective study of fractional limb volume for predicting fetal macrosomia in pregnancy affected by diabetes.

Objectives: To evaluate fetal thigh (TVol) and arm (AVol) fractional volume in pregnant women with pregestational diabetes (PGD) and normal glucose tolerance and to assess its ability to predict fetal macrosomia, defined as a birth weight of 4000 g or greater.

Methods: A single-center prospective cohort longitudinal study was conducted from February 2022 to November 2023. Women with a singleton pregnancy were enrolled in the study. Patients with severe extragenital pathology other than PGD, with fetal growth restriction, hemolytic disease, fetal malformations and anomalies, and gestational diabetes were excluded. The groups were those with PGD (n = 60) and the control group (n = 35). All patients underwent ultrasound examination three times during the third trimester, including standard biometry and assessment of fractional limb volume using 5D Limb Vol™ software (Samsung Medison). The primary outcome was a fetal macrosomia.

Results: Fractional limb volumes in the PGD group (TVol 64.8, AVol 30.2 mL) exceeded those in the control group (TVol 51.7, AVol 22.5 mL, P < 0.001). Large-for-gestational age fetuses had significantly higher TVol and AVol compared with appropriate-for-gestational age fetuses in both the PGD and control groups. Fractional thigh volume (TVol) measured within 7 days before delivery can predict fetal macrosomia with a sensitivity of 81.82% and a specificity of 84.93% at a cut-off of 82.71 mL.

Conclusion: Fetal limb fractional volume can be used as a predictor for fetal macrosomia in women having diabetes or normal glucose tolerance. Further investigation implementing automatized methods can improve estimated fetal weight assessment in birth weight extremes.