Ultrasonic measurement of fetal femoral length in singleton and twin pregnancies.

The fetal femoral length and biparietal diameter were measured by ultrasound on 1657 occasions in 1289 singleton pregnancies between 12 and 41 weeks' gestation. Mean values for fetal femoral length were significantly lower than those demonstrated in previous studies, with the difference becoming greater approaching term. Three hundred twenty-two measurements of fetal femoral length were made on 57 patients with twin pregnancies, with no significant difference noted between the means of these recordings and the means of the singleton pregnancies.