**7. Gastrointestinal system**

If the anomaly is large it may dislocate the mediastinal structures, causing polyhydramnios through the compression of the esophagus. It is often associated with other malformations

In pulmonary sequestration, the hamartoma usually gets its blood flow from the systemic circulation, either from the abdominal or the thoracic aorta. Most often small cysts (Type III) can be seen on the ultrasound, but it is important to prove the hamartomas connection to the systemic circulation. The intralobular form is more prevalent, but is less likely to get diagnosed. 90% of the extralobular cases are located in the left lower lobe and it is easier to detect [33, 34]. In diaphragmatic hernia, abdominal organs get through a defect of the diaphragm to the thorax. The incidence of this malformation is around 1:3700. 90% of the hernias are present on the left side. The defect itself, abdominal organs in the thorax and mediastinal shift can be detected with ultrasound. Pulmonary hypoplasia can also develop in severe cases due to the volume expansion

Malformations of the lungs were detected with a 52.94% sensitivity in our study, while dia-

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

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

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

phragmatic hernia cases were diagnosed with ultrasound in 86.79% of the cases.

important predictive factors for the outcome of these pregnancies [36, 37].

chance of a successful reposition of the organs is lower afterwards [5, 36, 40].

such as cardiovascular, urogenital, and skeletal anomalies or hydrocephalus.

in the thorax [5, 35].

10 Congenital Anomalies - From the Embryo to the Neonate

**6. Abdominal wall**

The fetal stomach can be visualized with ultrasound after 14 weeks. During the second and third trimester, the liver, gall bladder, spleen and intestines can all be examined with ultrasound in most cases. When the stomach cannot be seen it may suggest malformations such as esophageal atresia, diaphragmatic hernia, abdominal wall anomalies or neurological problems. When the filling of the stomach is not visualized during the examination, the ultrasound has to be repeated [5, 36].

Esophageal atresia is the absence of a part of the esophagus. The atresia is positioned higher than the trachea bifurcation in 85%, and a tracheoesophageal fistula is present in 90% of the cases. The birth prevalence of this malformation is around 1:3000. Signs on the ultrasound are polyhydramnios and the absence of the filling of the stomach. However, when a fistula is present, the stomach is filling, hence the low prenatal detection rate (10–40%) and late, third trimester diagnosis [14, 16, 34]. Later on, at around 24 weeks of pregnancy, the dilatation of the proximal end may be seen. About half of the cases are associated with other malformations, aneuploidy in 20%, growth retardation in 40% and most often with cardiovascular anomalies. Therefore, performing echocardiography and cytogenetic examination is important [5, 36, 41, 42].

The appearance of the intestines changes with the development of the fetus. Increased echogenicity of the fetal intestines can be a normal variant, but can also appear after the ingestion of blood. An increased echogenicity (as high as the bones) may appear in gastrointestinal malformations, Down-syndrome, cystic fibrosis or congenital infections (such as cytomegalovirus) [5, 36, 43].

Duodenal atresia may occur due to a real atresia, membranous closure or compression (annular pancreas) of the duodenum. The incidence of this condition is around 1:6000–1:10,000 birth. One-third of the cases are associated with Trisomy 21 and 50% develop as part of multiplex malformations. The specific ultrasound finding for duodenal atresia is the "doublebubble" sign. The two bubbles are the distended stomach and proximal duodenum. Usually polyhydramnios also appears. Echocardiography and cytogenetic examination is needed to detect the associated anomalies [5, 36].

Intestinal atresia only affects the small intestines in 95% of the cases with an incidence of 1:10,000 live birth.

Morphological types:


occur. The cysts are too small to be detected with ultrasound, but the enlargement and hyperechogenicity of the kidneys are seen. Furthermore, oligohydramnios and the absence of the filling of the bladder are also usually present. Potter-sequence may also appear due to the severe

Congenital Fetal Anomalies and the Role of Prenatal Ultrasound

http://dx.doi.org/10.5772/intechopen.71907

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In multicystic renal dysplasia, there is no normal parenchyma, but 10–20 mm cysts and connective tissue fill the kidneys. The anomaly is unilateral in two-third of the cases. The quantity of the amniotic fluid is usually normal, but oligohydramnios can appear in bilateral and sometimes polyhydramnios in unilateral cases. The incidence of this malformation is around 1:10,000 birth and it is more prevalent in boys. Most cases are diagnosed with ultrasound at 18 weeks as the cysts can be visualized and they are not connected to the renal pelvis. Also, the kidneys usually have an abnormal shape. Bilateral dysplasia is often fatal

Obstructions of the urinary tract usually results in the dilatation proximally. Obstruction of the ureteropelvic junction is the main cause of hydronephrosis in the neonate. Pyelectasis is the dilatation of only the renal pelvis and the calyces, while when the parenchyma is also affected by the compression, we talk about hydronephrosis. The dilatation of the pyelon and calyces can be seen in pyelectasis, while hydronephrosis appears as a solid cyst or sac. Pyelectasis is defined as a pyelon larger than 4 mm before 20 weeks or larger than 7 mm after 34 weeks of gestation. The anomaly is often diagnosed (2–5.5% of all fetuses), but spontaneous regression is common

In the obstruction of the ureterovesical junction, the ureter distends as well, creating a megaloureter. This anomaly is 4 times more prevalent in boys. In the presence of a posterior urethral valve, the bladder, ureter and renal pelvises dilate too and the distention damages the kidneys as well. It may cause severe oligohydramnios and Potter-sequence. Also, the dilated organs may stretch the abdominal wall, causing rectus diastasis (prune belly syndrome) [5, 44, 45].

Ovarian cyst is the most common abdominal mass in female fetuses with a birth prevalence of 1:2600. The malformation is more and more often diagnosed prenatally. The etiology of the anomaly is unknown and the cyst is usually benign. Ovarian cysts are more prevalent in fetuses of mothers with diabetes, eclampsia or Rh isoimmunisation. Complications are rare: compression of other organs, rupture, bleeding. The most common complication is the torsion of the

Malformations of the female organs are mostly caused by the impaired development of the Müllerian duct. When the two ducts do not fuse properly it causes the female organs to be septate or doubled. MRKH (Mayer-Rokitansky-Küstner-Hauser) syndrome is a malformation of the Müllerian duct when the upper two-third of the vagina and the uterus are

Malformations of the urogenital tract were diagnosed with ultrasound in 54.55% of the cases. The sensitivity of the ultrasound was high in polycystic kidney (100%), obstructions of the urinary tract (88.89%), multicystic renal dysplasia (80.57%), and pyelectasis (67.21%). However, genital malformations were harder to diagnose and a correct diagnosis was made

cyst may cause the ischemia and eventually necrosis of the ovary [47, 48].

oligohydramnios [5, 44, 46].

[44–46].

[6, 7, 45, 47].

missing [49].

in only 19.7% of the cases.


Intestinal atresia mostly occurs due to teratogenic effects. Polyhydramnios and dilated intestinal loops are usually seen on ultrasound. Atresia of the large intestines and of the anus is harder to detect due to the lack of polyhydramnios and less distended intestines. The dilated rectum that is filled with water may be visualized between the sacrum and the bladder [5, 36, 43].

Hirschsprung's disease is a congenital aganglionosis of the intestines that causes the distal large intestines to dilate. It occurs in 1:5000 live birth, mostly in boys. Dilated intestines and polyhydramnios are the most important signs on ultrasound after the second trimester. However, it is hard to differentiate between Hirschsprung's, cystic fibrosis and the atresia of the large intestines based on the ultrasound findings [5].

In our study, duodenum atresia was diagnosed with a high sensitivity of 94.74%, while atresia of the esophagus was diagnosed in only one-fifth of the cases.
