Measurements of fetal limb bones in early pregnancy

The fetal humerus, radius/ulna, femur, tibia/fibula and foot were measured in 296 pregnant women at 64-108 days' menstrual age, using vaginal sonography. All limb measurements correlated significantly with gestational age and biparietal diameter independently. Ratios of limb segment lengths did not change with gestation. Reference ranges (mean and 95% data intervals) were constructed for each limb segment. These data may prove useful in prenatal diagnosis of skeletal dysplasias and in the antenatal assessment of patients at risk of chromosomal abnormalities.