Ultrasonography is able to detect some fetal abnormalities as early as the first trimester of pregnancy. Using high-resolution ultrasound equipment, it is possible to demonstrate physiologic herniation of the midgut, which usually occurs between eight and nine weeks' gestation (calculated by last menstrual period). Fourteen cases have been studied with weekly ultrasound examinations between seven and 12 weeks' gestation. This herniation varied to a large extent in the different embryos depending on the amount of protruding intestine. In embryologic terms, the return of the intestine into the peritoneal cavity, and its rotation and fixation to the posterior abdominal wall, should be concluded at ten to 12 weeks. In all cases studied, the persistence of umbilical herniation could be ruled out by sonographic visualization of the umbilical cord insertion between ten and 12 weeks. Therefore, the suspicion of a severe congenital abdominal wall defect, such as omphalocele, umbilical herniation, or gastroschisis can reliably be confirmed only after 12 weeks' gestation.
© 1987 The American College of Obstetricians and Gynecologists