Transvaginal sonography at 5 to 14 weeks' gestation: fetal stomach, abnormal cord insertion, and yolk sac.

Transvaginal ultrasound evaluation of the fetal digestive system was performed on 1000 fetuses at 5 to 14 weeks' gestation. The normal physiologic process of the midgut herniation into the cord as well as the embryonal connection between the yolk sac and fetus were detected. Peristalsis of the stomach was noted as early as 14 weeks' gestation. Because gastric emptying is probably improper at this age, gastric pseudomasses were visualized in some cases.