Composite assessment of gestational age: a comparison of institutionally derived and published regression equations.

Abstract

This study was undertaken to evaluate (1) the applicability of previously reported regression equations for gestational age assessment to our patient population in Pittsburgh and (2) whether the addition of radius length or its substitution for one of the other fetal measurements could improve the prediction of gestational age. Five fetal parameters--biparietal diameter, head circumference, abdominal circumference, femur length, and radius length--were measured in a prospective cross-sectional study of gestational age assessment in 265 pregnant women between 13 and 43 weeks' gestation. The regression equation derived for each fetal parameter was found to be quite similar to previously published reports. Although the coefficient of determination was only minimally affected, the variability improved with the institutionally derived regression equation. The incorporation of several fetal measurements into a composite assessment of gestational age generally enhances the accuracy of the prediction. The addition of a second long bone to a gestational age assessment does not significantly improve results.