Charts of fetal size: limb bones.

OBJECTIVE To construct new size charts for all fetal limb bones. DESIGN A prospective, cross sectional study. SETTING Ultrasound department of a large hospital. SAMPLE 663 fetuses scanned once only for the purpose of the study at gestations between 12 and 42 weeks. METHODS Centiles were estimated by combining separate regression models fitted to the mean and standard deviation, assuming that the measurements have a normal distribution at each gestational age. MAIN OUTCOME MEASURES Determination of fetal limb lengths from 12 to 42 weeks of gestation. RESULTS Size charts for fetal bones (radius, ulna, humerus, tibia, fibula, femur and foot) are presented and compared with previously published data. CONCLUSIONS We present new size charts for fetal limb bones which take into consideration the increasing variability with gestational age. We have compared these charts with other published data; the differences seen may be largely due to methodological differences. As standards for fetal head and abdominal measurements have been published from the same population, we suggest that the use of the new charts may facilitate prenatal diagnosis of skeletal dysplasias.