Assessment of foetal femur length by ultrasound in a normal Nigerian obstetric population.

In a group of Nigerian pregnant women at different gestational ages, 1097 foetal femur length measurements were taken using ultrasound. The measurement increased from a mean femur length of 15.9 mm at 14 weeks' gestation to 75.0 mm at 40 weeks' gestation. The growth pattern showed an asymptotic curve with faster growth in the early part of pregnancy. The standard deviation widened towards 40 weeks of gestation. There was a statistically significant correlation (r = 0.9887; P less than 0.001) between gestational age and femur length. In the first half of pregnancy the femur length was significantly smaller than in studies reported for Caucasians. The finding may be related to the habit of late booking for antenatal care in our patients.