**3.1. Velamentous insertion of the cord**

The umbilical cord insertion is located on the placental mass in about 99% of cases, into the central portion of the placenta. The velamentous insertion is the condition in which the umbilical vessels are configured between amnion and chorion before reaching the placenta on the chorioamniotic membranes [31]. That abnormal insertion occurs when the cord implants in the trophoblast anterior to the decidua capsularis or when placental tissue grows laterally, leaving an area which becomes atrophic. The umbilical cord inserts into the chorion leave at a point away from the placental mass and appears as membranous umbilical vessels at the placental insertion site (velamentous vessels are not protected by Wharton's jelly), the rest of the cord is usually normal. This type of pathological insertion of the cord occurs in 1–2% of singleton pregnancies. In multiple pregnancies, the incidence of velamentous cord insertion is 10-fold higher than in singleton pregnancies [32] (**Figure 6**).

Heinonen et al. [33] in this aberrant attachment, such as at the margins or to the membranes, found an association with higher maternal serum human chorionic gonadotropin (hCG) and lower maternal serum alpha-fetoprotein (AFP). However, until further data is available, no specific recommendations can be made.

Prenatal identification of these pregnancies is an important issue. There is a higher risk for an adverse perinatal outcome like intrauterine growth retardation, preterm birth, placental abruption, vasa previa, low Apgar scores at 1 and 5 min, neonatal death, congenital anomalies, and fetal bleeding [34]. Associated anomalies include trisomy 21, spina bifida, ventricular septal defects, esophageal atresia, obstructive uropathies, congenital hip dislocation, and asymmetrical head shape. It has been noted that a higher rate of deformations occur instead of malformations or disruptions [34]. Velamentous insertion associated with vasa previa appears to have an increased rate of congenital malformations. Also, 13% cases of single umbilical artery are associated with velamentous insertion [14].

**Figure 6.** Velamentous cord insertion.

**2.3. Four-vessel umbilical cord**

Five percent of umbilical cords exhibit a four-vessel structure due to the persistence of small vitelline arteries, which follow the normal twisting of the main umbilical arteries. [28].

Four umbilical vessels view is an abnormal situation that has been reported to be associated with major congenital anomalies [29]. The presence of three umbilical arteries is the most common situation of four-vessel cord, although in the specialty literature have been reported

The insertion of umbilical cord can be located following the chorionic plate vessels using color Doppler technique. The placental insertion of the UC is better observed by ultrasound in the first trimester. Later when gestational age increases, visualization becomes difficult, especially when the placenta is posterior. The evaluation of fetal circulation is done by examining the umbilical arteries. The umbilical vascular evaluation provides information on the circulation at the fetomaternal interface level, giving the possibility of early detection of risk to the fetus [19].

The umbilical cord insertion is located on the placental mass in about 99% of cases, into the central portion of the placenta. The velamentous insertion is the condition in which the umbilical vessels are configured between amnion and chorion before reaching the placenta on the chorioamniotic membranes [31]. That abnormal insertion occurs when the cord implants in the trophoblast anterior to the decidua capsularis or when placental tissue grows laterally,

a few cases of cord with two umbilical veins and two umbilical arteries [30].

**3. Abnormal course or connection of vessels**

**Figure 5.** Persistent right umbilical vein (*Dao,* descending aorta).

350 Congenital Anomalies - From the Embryo to the Neonate

**3.1. Velamentous insertion of the cord**

#### Vasa previa

It is important to be aware that velamentous cord insertion is associated with an increased rate of vasa previa. Vasa previa is a form of velamentous cord insertion in which velamentous vessels pass through the fetal membranes of the lower uterine segment and incidence is estimated to be 0.04% [35]. These fetal vessels may break when membrane rupture occurs and the result is fetal exsanguination. Intrapartum diagnosis is very difficult in this case [36].

**4.2. Umbilical vein varix**

controversial.

**4.3. Umbilical artery aneurysm**

ated with umbilical artery aneurysm.

appears to be similar to that of second-trimester cysts [47].

pressure in the umbilical vessels (**Figure 8**).

Tumors of the Umbilical Cord

**4.4. Cord cysts**

Umbilical vein varix is a rare condition which occurs in the intrahepatic portion of the umbilical vein presents an incidence of 2.8:1000 [39]. Ultrasound scan usually discovers a circular vessel dilation ≥ 9 mm, 59 or more than 50% over the diameter of the intrahepatic UV [40]. The condition is associated with chromosomal anomalies in up to 12% of cases, especially trisomy

Abnormalities of the Umbilical Cord http://dx.doi.org/10.5772/intechopen.72666 353

Complete follow-up includes karyotyping, regular fetal testing, and third trimester interval growth studies [42]. Because the incidence is very low, the clinical significance remains

Umbilical artery aneurysm is an extremely rare vascular anomaly usually associated with high risk of fetal aneuploidy, IUGR, and fetal demise. Fetal demise is a result of compression of the dilated artery on the umbilical vein, thrombus formation, or due to associated fetal anomaly like trisomy 18 [43]. This condition is a vascular anomaly which appears as an anechoic cyst close to cord insertion with a hyperechogenic rim in which color flow and spectral Doppler examinations show nonpulsatile and turbulent blood flow within the artery [44]. It is important to consider karyotype analysis given the high incidence of aneuploidy associ-

Cord cysts have no clinical relevance and develop from the remnants of the allantois or the omphalomesenteric duct. The finding of an isolated umbilical cord cystic mass should lead to further detailed sonographic evaluation and karyotype testing should be done when IUGR or other anomalies are found [45]. The majority of first-trimester cysts are transient ultrasound findings that have no influence on pregnancy outcome [46]. The prognosis of persistent cysts

Several studies concluded that morphologic features of cord cyst (single, multiple) correlate

Umbilical cord cysts are classified as true cysts or pseudocysts. True cysts have an incidence of 3.4% in first trimester of pregnancy and have no clinical significance, and are sometimes associated with fetal structural anomalies and aneuploidy [45]. True cysts are derived from the embryological remnants of either the allantois or the omphalomesenteric duct, are located

The exact cause of umbilical cyst is not known, but it is thought to be due to raised hydrostatic

typically toward the fetal insertion of the cord and range from 4 to 60 mm in size [49].

with fetal abnormalities like abdominal wall defects and patent urachus [48].

21and poor fetal outcome with emergent cesarean delivery [41].
