When ultrasonography reveals a fetal abdominal wall defect
Although these fetal defects are rare, be alert to their potential presence when early ultrasonography indicates structural abnormalities. Here, surveillance, planning, and appropriate patient counseling are reviewed.
Making the diagnosis
Prenatal diagnosis using ultrasonography is possible at around 10 weeks of gestation. As previously mentioned, however, physiologic herniation of the midgut must be excluded by performing follow-up imaging at a later gestational age. In our practice, we typically do this at around 16 weeks of gestation.
Ultrasonographic features of gastroschisis include loops of bowel herniating through a small paraumbilical wall defect (usually 2–3 cm) floating in amniotic fluid without a covering membrane4 (FIGURE 2). Direct exposure to amniotic fluid causes small bowel inflammation and fibrin deposition, leading to a thickened, echogenic appearance. Polyhydramnios and intra-abdominal bowel dilation have been associated with the presence of intestinal atresia.10
Management
There is no expert consensus regarding optimal prenatal management of gastroschisis.11-17 Prenatal care, patient counseling, and delivery planning should be individualized based on the defect and should be determined in a multidisciplinary discussion with specialists in maternal-fetal medicine, neonatology, and pediatric surgery, as necessary. In our practice, if the gastroschisis is isolated and uncomplicated, our generalist obstetricians manage the patient with maternal-fetal medicine consultation, increased fetal surveillance as described below, and delivery at our tertiary care institution.
Our standard practice is to use the initial ultrasonography imaging to evaluate the size and contents of the defect, measure the nuchal translucency, and evaluate for additional abnormalities. Serial ultrasonography monitoring of the fetus is required to assess the size and quality of the herniated intestine, amount of amniotic fluid, and fetal growth.10
As gastroschisis is a full-thickness defect of the anterior abdominal wall, the abdominal contents are exposed to amniotic fluid. This exposure causes progressive intestinal damage, which can be identified on ultrasonography as bowel thickening and dilation.12-14 Currently, intestinal thickening and dilation is not considered an indication for delivery as it is assumed that the intestinal damage has already occurred. It is debatable whether delivery around 37 weeks compared with delayed delivery beyond 37 weeks improves outcomes and decreases the stillbirth rate.11,13 Studies show that neonates delivered prior to 37 weeks have worse outcomes compared with those delivered after 37 weeks.14,15
Fetal surveillance. As standard practice, we evaluate the fetus at around 16 weeks and then again at around 20 weeks. In the absence of fetal growth restriction, which is associated with 25% of cases,16,17 our standard practice includes performing serial growth ultrasonography every 3 to 4 weeks starting at 28 weeks and biophysical profiles and nonstress testing weekly starting at 32 weeks. Fetal echocardiography can be offered. However, unlike with omphalocele, which has a high incidence of associated cardiac structural anomalies, gastroschisis has a low incidence of congenital cardiac anomalies, estimated to be between 2.5% and 4%.18,19
Delivery considerations. Little agreement exists regarding when and how to deliver pregnancies complicated by fetal gastroschisis. While some advocate for induction of labor at 36 to 38 weeks, most infants with gastroschisis can be delivered safely at term via either vaginal or cesarean delivery.14,15
Delivery timing should consider the clinical picture and incorporate performance on antenatal testing, fetal growth, the size and contents of the gastroschisis, and consultation with maternal-fetal medicine. Fetuses with gastroschisis often have non-reassuring antenatal testing. This can necessitate early delivery, although cesarean delivery should be reserved for obstetric indications, with the caveat that if there is large liver involvement, some pediatric surgeons recommend cesarean delivery due to the risk of hepatic rupture.
Neonate management. The survival rate of gastroschisis is reported to be as high as 91% to 94%.2 Morbidity is related to intestinal complications, such as strictures, adhesions, and volvulus.
In the case of simple gastroschisis, when the bowel is in good condition, the treatment method of choice is primary reduction.20 If performed in the operating room, an immediate sutured closure of the defect can be done. The benefits of primary repair include decreased length of stay, fewer intensive care bed days, and less time to achieve full feeds.20,21 Primary reduction has a reported success rate of 50% to 83%.22 A reduction with a delayed spontaneous closure also can be performed at bedside in the neonatal intensive care unit.22
For complex gastroschisis, characterized by bowel complications such as inflammation, perforation, ischemia, atresia, necrosis, or volvulus, primary closure may not be possible and reduction may need to be achieved through silo application.22-25 Additionally, further bowel surgery, such as stoma formation and bowel resection, may be required.25
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