**6. Abdominal wall**

Abdominal wall malformations (omphalocele, gastroschisis) are fairly prevalent malformations. Maternal serum alpha-fetoprotein level is often elevated in these malformations and intrauterine growth restriction (IUGR) is frequently present. IUGR and the involvement of the liver are important predictive factors for the outcome of these pregnancies [36, 37].

In gastroschisis, there is a defect on the abdominal wall that affects all the abdominal layers, including the amnioperitoneal membrane. It usually appears on the right side of the umbilical cord, but does not involve the cord itself. Gastroschisis has an incidence of 1:2000–1:5000 and is more prevalent in the fetuses of younger mothers. Gastroschisis is always associated with polyhydramnios. The efficacy of ultrasound in this anomaly is around 80% at 18–20 weeks [38, 39]. In early diagnosis, termination of pregnancy is an option and when diagnosed later, it is important to follow-up on the condition of the intestines and deliver the baby if signs of necrosis appear. Cesarean section is suggested in all cases, because vaginal delivery pose a higher risk of infection of the abdominal organs. The fetus is delivered before 35 weeks of pregnancy, because the chance of a successful reposition of the organs is lower afterwards [5, 36, 40].

In omphalocele, abdominal organs herniate into the amniotic fluid through the umbilicus. The defect is always associated with polyhydramnios, it is medially positioned and the organs are covered by the amnioperitoneal membrane. Omphalocele has an incidence of 1:6000 live birth. Herniation of the abdominal organs to the umbilical cord is normal before 11 weeks, but the defect usually closes by then. Therefore, omphalocele can be only detected with second trimester ultrasound at 18–20 weeks. The sensitivity of prenatal ultrasound in the diagnosis of this anomaly is around 75–90% [6, 7, 38, 39]. Performing echocardiography or cytogenetic examination is justified in these fetuses as omphalocele is associated with other malformations and chromosomal abnormalities in more than half of the cases. The smaller the defect is, the higher the risk of aneuploidy is. When there is no associated malformation, the pregnancy can be carried to term [40].

Abdominal wall malformations were diagnosed with a high sensitivity in our study. All gastroschisis (12/12) and most of omphalocele (25/33, 75.76%) cases were diagnosed antenatally.
