Can 3D volumetry of the fetal upper arm and thigh improve conventional 2D weight estimates?

Aim: To determine the usefulness of three-dimensional ultrasound volumetry of fetal thigh and upper arm in predicting weight at delivery. Method: Incl usion criteria to our prospective study were singleton pregnancies with a p lanned or expected delivery within 96 hours of enrollment. In 74 patients ( formula-finding group) standard fetal biometry, followed by measurement of thigh and upper arm volumes by three-dimensional ultrasound, was performed. Subsequently, our new 3D-formulas were tested in a prospective validation group of 52 patients. Results: Both upper arm and thigh volumes correlated well with birth weight (r(2)=0.95, respectively, p<0.0001). The best result , however, was achieved by a combination of standard 2D-measurements with t he volumetric data of upper arm and thigh (r(2)=0.98, p < 0.0001). With use of polynomial regression analysis we obtained two best-fit formulas: Birth weight: - 263.8 + 13.7269 * Arm Volume + 7.16575 * Thigh Volume + 148.2 * ATD. Birth weight: 1288.7 + 51.9502 * Arm Volume - 0.252 * Arm Volume(2) -2 .1766 * Thigh Volume + 0.0321 * Thigh Volume(2) + 36.2509 * GA 0.7526 * GA( 2)+ 654.3 * BIP-36.6136 * BIP2- 381.8 * ATD + 24.0927 * ATD(2). Conclusion: Three-dimensional volumetry of the fetal thigh and upper arm may improve p rediction of birth weight. Further larger studies are needed to validate ou r results.