Prediction of birth weight in twin pregnancies using fractional limb volumes by three-dimensional ultrasonography.

OBJECTIVE: To predict birth weight using fetal fractional limb volumes by three-dimensional (3D) ultrasonography in twin pregnancies.

METHOD: This prospective observational cohort study evaluated 51 twin pregnancies, including 28 dichorionic and 23 monochorionic pregnancies. Ultrasound examinations were performed up to 5 days before delivery. Birth weight prediction models were developed using the fractional arm volume (FAV), fractional thigh volume (FTV), and Hadlock's formula and were compared with the actual birth weight.

RESULTS: The mean gestational age at the time of ultrasound examination was 35.3 weeks. The mean birth weight was slightly higher in dichorionic than in monochorionic pregnancies 2391.2 versus 2352.4 g. The measurements using FTV were the closest to actual birth weights. For the total group, the Hadlock formula had mean percentage change of 7.18% while the FTV model presented mean percentage change of 6.62% in relation to birth weight. However, no significant difference was noted between Hadlock's formula and FTV p = 0.363 and 0.678 for dichorionic and monochorionic pregnancies, respectively.

CONCLUSION: FTV accurately predicted birth weight in twin monochorionic and dichorionic pregnancies. However, Hadlock's formula should still be used.