Correlation of biparietal and fetal body diameters: 12--26 weeks gestation

One hundred thirty-four obstetrical diagnostic sonographic examinations were performed on patients of 12--26 gestational weeks. The following abdominal diameter measurements were obtained: (1) anteroposterior transverse diameter; (2) right-to-left transverse diameter; (3) average of (1) and (2); and (4) greatest longitudinal diameter. These measurements were plotted against the respective biparietal diameters, and normal statistical distribution curves were developed. These curves have proven helpful in cases with a questionable disproportionate relation between the fetal head and body size in early pregnancy. The data have facilitated identification of fetal abnormalities sufficiently early in the pregnancies to permit advising therapeutic abortion. Five cases outside the normal range are discussed and compared to normal. In several cases, the sonographic results played a major role in the decision-making process of the patient involved.