An evaluation of fetal weight prediction using a simple equation containing the fetal femur length.
The accuracy of sonographic fetal weight estimation based on five published regression equations and two new equations generated from data at the authors' institution was evaluated on 41 small-for-gestational age (SGA) fetuses and 57 appropriate-for-gestational age (AGA) fetuses. Equations which contained the fetal femur length (FL) in addition to the biparietal diameter (BPD) and abdominal circumference (AC) yielded lower systematic and random errors in the SGA group but not in the AGA group. These findings support the contention that consideration of the FL is important in sonographic estimation of fetal weight in the growth-retarded fetus as head and limb growth may be affected to different degrees in different fetuses. A new equation, where birthweight in grams = 1.4 X (BPD(cm) X AC(cm) X FL(cm)) - 200, was developed which had a standard deviation of 98 g/kg in SGA fetuses and 68 g/kg in AGA fetuses. This equation yielded significantly lower random errors in the SGA but not in the AGA fetuses when compared with another linear equation without the FL. The new model is simple and practical to use, which makes it a viable alternative to more elaborate models containing three parameters.
D000005:Abdomen / Q000033:anatomy & histology; D001835:Body Weight; D005069:Evaluation Studies as Topic; D005260:Female; D005269:Femur / Q000033:anatomy & histology*; D005333:Fetus / Q000033:anatomy & histology*; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D011247:Pregnancy; D011336:Probability; D012044:Regression Analysis; D012886:Skull / Q000033:anatomy & histology; D014463:Ultrasonography