**1. Introduction**

Abdominal wall defects (AWDs) define a type of congenital anomalies characterized by the herniation of abdominal organs through an unusual opening surrounding the umbilical cord. The most common two types include omphalocele and gastroschisis. The omphalocele or exomphalos (in Greek, omphalos = umbilicus, kele = hernia, tumors) was firstly described in 1634 by Ambroise Pare, while gastroschisis (in Greek gastro = stomach—the term generally

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used for abdomen; schisis = fissure, tear or gape) was first described by James Calder, a decade later. Other uncommon AWDS are ectopia cordis (EC), limb–body wall complex, cloacal and bladder exstrophy, urachal cyst, Prune belly syndrome and Cantrell pentalogy [1]. The correct prenatal detection and classification of these fetal malformations are extremely important for subsequent opportunities in parental counseling and pregnancy management. Nowadays, the intensive use of US assessment has allowed an increase in detection rates of AWDs, even from the first trimester nuchal translucency scan.

The prevalence of the two most frequent entities of AWDs is reported to be for gastroschisis 3.09 per 10,000 births, with a live birth prevalence of 2.63 per 10,000 and for omphalocele 3.29 and 1.13 per 10,000, respectively [21]. The prevalence of gastroschisis has increased in the last years, whereas that of omphalocele has remained stable [22]. Regarding the prenatal diagnosis of AWDs, both omphalocele and gastroschisis are easily diagnosed at the 11–14 weeks nuchal scan. So, large studies report sensitivity for both congenital anomalies from 90 to 100% [23, 24]. In fact, reports show that 22 and 35% of the chromosomally normal cases of gastroschisis and omphalocele, respectively, were diagnosed before 14 weeks, and 50 and 30% between 14 and 23 weeks. The overall prenatal detection rate was 91.6% for gastroschisis and

Fetal Abdominal Wall Defects

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http://dx.doi.org/10.5772/intechopen.71936

**3. Prenatal diagnosis and classification of fetal abdominal wall** 

Gastroschisis is an AWD characterized by the herniation of the abdominal viscera represented by bowel loops and occasionally parts of other abdominal organs outside the abdominal wall with no covering membrane or sac, to the right of the insertion of the umbilical cord, and rarely to the left side [25, 26]. Even if the condition is not generally associated with other major congenital or chromosomal anomalies, an accurate fetal anatomy assessment is required. The reported rate of the proportion of gastroschisis associated with major defects is about 10% [27], arthrogryposis being present in a minority of these fetuses [28], with a reported mortality rate of 5–10% in all cases of gastroschisis [29]. Others report a higher rate (14%) of additional associated anomalies, the central nervous system and cardiac malformations being the most common anomalies [30]. Gastroschisis is often classified into simple (as an isolated defect) and complex (as associated with bowel-related complications: intestinal atresia, perforation, stenosis or volvulus) [31]. In cases with intestinal complications, there is a relevant risk of increased morbidity, higher rates of complications, as respiratory distress or sepsis and of course an increased length of hospital stays [32]. The key to an accurate diagnosis is fetal US in routine antenatal care, which affects patient management and prognosis. In the past, the detection was higher in the second trimester, between 16 and 22 weeks of gestation, in approximately 60% of cases, with a false positive rate of 5.3% [33]. Misdiagnosis of gastroschisis as omphalocele has serious implications, as gastroschisis is rarely associated with chromosomal anomalies and unnecessary amniocentesis may be needed with additional risks to the procedure [34]. Nowadays, the diagnosis of gastroschisis can be facilitated ultrasonographically as early as the late first trimester, 12–13 weeks of gestation [35]. After correctly identifying a normal umbilical cord insertion using color Doppler, gastroschisis is detected as herniation of the bowel loops with no covering membrane (e.g. **Figure 1a**). In most cases, the defect is on the right side of the umbilical cord with a normal umbilical cord insertion. Beside the location of the defect, it is important to establish the size and content of the defect and if

83.3% for omphalocele [21].

present, the associated anomalies.

**defects**

**3.1. Gastroschisis**
