title: Ultrasound fetal thigh-calf circumferences and gestational age--independent fetal ratios in normal pregnancy.
abstract: The growth of the sonographically measured fetal thigh and fetal calf circumferences was studied during normal pregnancy. The normal range of fetal thigh and fetal calf circumferences for each week of pregnancy was determined from 20 to 41 weeks. The ratios of the ultrasonically measured fetal femur length to thigh circumference (expressed as femur length/thigh circumference X 100) and fetal tibia length to calf circumference (expressed as tibia length/calf circumference X 100) were also determined. These ratios were found to be relatively constant, with normal ranges after 20 weeks of 51.8 +/- 7.8 and 57.6 +/- 9.4 (mean +/- 2SD) respectively. The applications of these new fetal parameters in the evaluation of abnormal fetal growth patterns are discussed. It is suggested that these ratios should be used in evaluating fetal growth in high-risk patients who present late in pregnancy with unknown dates.
mesh_terms: D000886:Anthropometry; D005314:Embryonic and Fetal Development; D005260:Female; D005865:Gestational Age; D006801:Humans; D007866:Leg / Q000196:embryology*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D013848:Thigh / Q000196:embryology; D014463:Ultrasonography; D014894:Weights and Measures