Consecutive ultrasonic measurements of the fetal head area, thorax area, abdomen area, head/thorax (H/T) area ratio and head/abdomen (H/A) area ratio were obtained from 100 patients with a normal pregnancy and from 186 patients with suspected intrauterine fetal growth retardation. Of all the measurements used, H/A area ratio was found to be most accurate in identifying intrauterine fetal growth retardation predicting 82.9 per cent at 33 weeks and 85.7 per cent at 36 to 38 weeks of gestation. This technique was also found to be useful in distinguishing between the two types of growth retardation. The H/A area ratio was helpful in identifying the growth acceleration pattern of a large baby. 623