[Ultrasonic evaluation of fetal weight by comparing the circumference and area of the trunk].

Birthweight estimation has clinical importance in routine practice. The method used at present is the measuring of the circumference of the fetal abdomen at the umbilical vein level. The aim of this study was to check the theoretical hypothesis that a simple method of the trunk area measurement is a better birthweight estimator than the circumference measurement (when elliptic elongation is changed). In order to make this measurement simple, an ellypsoid approximation of the trunk cross section was used, i.e. the longest and the shortest diameters were measured. The area is proportional to the product of the diameters while the circumference is proportional to the sum of the two. The longest and the shortest diameters were measured in 200 patients up to two days prior to delivery, perpendicular to the spine at the umbilical vein level. The results have shown that in fetuses whose cross-section of the abdomen is elongated, the product of the longest and the shortest diameter gives a significantly better correlation to birthweight than their sum.