Growth of the ultrasound fetal femur length during normal pregnancy. Part I.

The growth of the ultrasound fetal femur length during normal pregnancy is presented. A total of 1,016 measurements of the fetal femur length from 14 weeks' gestation through term were taken. The growth of the fetal femur describes an asymptotic curve similar to the growth of the biparietal diameter with comparable limits of 2 SD. From the serial measurements performed, the growth rate of the femur has also been calculated. This begins at 3.15 mm/wk and slowly decreases to 1.55 mm/wk toward 40 weeks' gestation. Femur measurements provide the first reproducible determinations of "length" of the fetus to be measured by ultrasound throughout pregnancy.