[Determination of the gestational age in late pregnancy by sonography (author's transl)].

In 219 normal pregnancies between 28 and 42 weeks the relationships of different ultrasound measurements of the fetal head and the fetal body to the gestational age were determined in order to improve the accurate diagnosis of fetal maturity during the last trimester of pregnancy. With the A and B ultrasound apparatus of Kretz, the biparietal diameter was determined by the A mode, the fronto occipital plane and the largest abdominal diamter were determined by the B scan. The following ultrasound measurements were taken: the two horizontal and transverse diameters, the circumferences and the planes. The abdominal measurements showed a higher rate of growth, compared to the cranial measurements a lesser rate of growth retardation and a higher variation of the normals. The correlation of the abdominal measurements with the gestational age was worse than that of the cranial measurements. Wth the exception of the biparietal diameter in the A mode, the mean diameters of the cranial and abdominal measurements gave better results than the single diameters. Circumference and surface measurements showed no advantages. The best results were obtained by combined fetal head and body measurements using the summation of the biparietal diameter in the A mode and the mean abdominal diameter in the B scan.