RESUMO
With the aid of the ultrasound scan technique the amniotic sac was measured on more than 700 occasions between the 8th and 20th week of gestation. In each examination the greatest transverse, anterior-posterior and longitudinal diameters were determined. The statistical mean and the double standard deviation were calculated from these data. The areas of the transverse diameter and of the longitudinal diameter show a distinct and continuous increase, whilst the area of the anterior-posterior diameter displays a small and uncharacteristic increase during pregnancy. The values of 12 patients were registered in the region of the transverse and of the longitudinal diameter. The clinical findings, as well as the ultrasonic values, had shown no abnormalities at that time. The data show a decrease in these diameters during the following examinations; the last measurement was carried out when the fetal heart beat was absent for the first time. The increase in size of the amniotic sac during pregnancy can be observed by means of these examinations. Repeated examinations enable the detection of disturbances in the developement of the pregnancy at an early stage.