Fetal weight estimation by three-dimensional ultrasound

Abstract

Objective: To assess the value of three-dimensional volume scanning in predicting fetal weight at birth.

Study design: Prospective cross-sectional study within 7 days of delivery. A total of 190 patients were considered for final analysis (formula-finding group: n = 125, formula evaluation group: n = 65). Inclusion criteria were a singleton pregnancy and absence of chromosomal or significant structural anomalies. Three-dimensional (3D) volumetric measurements of the fetal thigh, upper arm and abdomen were performed together with conventional two-dimensional (2D) biometry.

Results: All measurements were completed successfully in each patient. Polynomial regression analysis with standard biometric parameters and volumes of the upper arm, the thigh and the abdomen was employed to yield the best-fit formula for prediction of fetal weight at birth. The new 3D formula (estimated fetal weight (EFW) = -1478.557 + 7.242 x thigh volume + 13.309 x upper arm volume + 852.998 x log10 abdominal volume + 0.526 x BPD3) proved to be superior to established 2D equations with the lowest mean error (25.8 +/- 194.4 g), the lowest mean absolute error (155.2 +/- 118.2 g) and the lowest mean absolute percentage error (6.1 +/- 5.0%) when studied prospectively in the evaluation group.

Conclusion: 3D sonography allows superior fetal weight estimation by including soft tissue volume. Further studies at the extremes of fetal weight are needed to confirm the value of our formula in these subsets.