**2.1. Single umbilical artery**

It seems that the first descriptions of the single umbilical artery were made in 1543 by Vesalius in De Humani Corporis [4]. It may be diagnosed with the finding of two vessels on a crosssection of the cord or a vessel seen on only one side of the fetal bladder. These anomalies appear to be more common when the left umbilical artery is absent and may be associated with aneuploid fetuses and renal anomalies in euploid fetuses. Atresia, aplasia, or agenesis of one artery can lead to single umbilical artery syndrome [5].

Single umbilical artery (SUA) is the most common abnormality of the umbilical cord.

There are three theories about the absence of umbilical artery pathogenesis: (1) primary agenesis of an umbilical artery; (2) atrophy or secondary atresia of the previously normally developed umbilical artery; and (3) persistence of the original allantoic artery of the body stalk [6]. It is suggested that from the embryological point of view, the second theory would be a reasonable explanation [7].

In single umbilical artery pregnancies, chromosomal abnormalities were found in 8–11% of fetuses, more commonly trisomy 13 and 18 and less frequently trisomy 21 [8], intrauterine growth restriction (IUGR), preterm birth, placental anomalies, and perinatal mortality [9, 10].

In rare cases, both umbilical arteries are missing and the one arterial vessel is, in fact, a persistent vitelline artery, which branches off the abdominal aorta. [11]. This persistent vitelline artery appears to be associated with serious developmental defects and was classified as type II single umbilical artery (type II SUA) by Blackburn and Cooley. This anomaly accounts for 1.5% cases of single umbilical artery [12]. According to the same authors, the most common form of single umbilical artery (98%) is type I that has one artery and one vein (left), whereas type II SUA has a frequency of 1.5%. Very rare forms are type III with one artery and two veins (left and persistent right umbilical vein) and type IV with one artery and one vein (right).

The umbilical cord structure can be demonstrated by conventional real-time ultrasound and the umbilical blood flow patterns can be analyzed by color (power) and pulsed Doppler ultrasound, which relate to its functionality [1]. Second trimester scan is able to assess four characteristics of the umbilical cord: measurement of umbilical cord area, evaluation of the number of vessels, assessment of placental umbilical cord insertion site, and determination of

Abnormalities of the umbilical cord related to morphology, placental insertion, number of vessels, and primary tumors can influence the perinatal outcome and may be associated with other fetal anomalies and aneuploidies. Many of these conditions are being diagnosed in

Using ultrasound, we can depict various congenital abnormalities of the umbilical cord, including cysts, pseudocysts, umbilical vein varix, persistent right umbilical vein, angiomyxomas, aneurysm, single umbilical artery (SUA), velamentous insertion, and teratomas.

Sometimes, during pregnancy, changes in the number of umbilical vessels may occur. Abnormal number of umbilical cord vessels includes: two-vessel cord (single umbilical artery), four-vessel cord (two veins and two arteries, one vein and three arteries), five and more vessels cord (numerous variations in conjoined twins), umbilical cord that does not keep

It seems that the first descriptions of the single umbilical artery were made in 1543 by Vesalius in De Humani Corporis [4]. It may be diagnosed with the finding of two vessels on a crosssection of the cord or a vessel seen on only one side of the fetal bladder. These anomalies appear to be more common when the left umbilical artery is absent and may be associated with aneuploid fetuses and renal anomalies in euploid fetuses. Atresia, aplasia, or agenesis of

Single umbilical artery (SUA) is the most common abnormality of the umbilical cord.

There are three theories about the absence of umbilical artery pathogenesis: (1) primary agenesis of an umbilical artery; (2) atrophy or secondary atresia of the previously normally developed umbilical artery; and (3) persistence of the original allantoic artery of the body stalk [6]. It is suggested that from the embryological point of view, the second theory would be a

In single umbilical artery pregnancies, chromosomal abnormalities were found in 8–11% of fetuses, more commonly trisomy 13 and 18 and less frequently trisomy 21 [8], intrauterine growth restriction (IUGR), preterm birth, placental anomalies, and perinatal mortality [9, 10].

utero as prenatal ultrasound becomes more sophisticated nowadays.

the same number of vessels at the fetal and placental extremity [3].

one artery can lead to single umbilical artery syndrome [5].

the coiling pattern [2].

**2. Abnormal number of vessels**

346 Congenital Anomalies - From the Embryo to the Neonate

**2.1. Single umbilical artery**

reasonable explanation [7].

There is an increased incidence of severe malformations associated with type II SUA with the implication of the caudal body wall (sirenomelia, omphalocele-exstrophy-imperforate anus-spinal defects) and urorectal like exstrophy of the bladder, anal atresia, or urogenital agenesis [13].

Among pregnancies with single umbilical artery associated with various malformations, twothirds of deaths occur before birth. Regarding the other third of postnatal deaths, an increased incidence of fetal growth restriction and small placental size was found [14].

If no additional chromosomal or structural abnormalities occur, single umbilical artery is defined as an isolated SUA (iSUA) [10], and more than 90% of cases with SUA exhibit an isolated anomaly but without increasing the risk of chromosomal abnormalities [15]. Regarding adverse pregnancy outcomes and perinatal complications, studies show discordant results. A meta-analysis suggests that there is no significant association between iSUA and pregnancy outcomes [16, 17], while another meta-analysis suggests that iSUA is associated with a significant increase in adverse perinatal outcomes [18].

Single umbilical artery can be diagnosed in the first trimester using color Doppler and highdefinition ultrasound with a low pulse repetition frequency (PRF) and a high color gain. Visualization of the umbilical arteries is preferable at the level of the fetal urinary bladder (**Figure 1**) by demonstrating the cord's perivesical course [19].

In conclusion, the easiest way to assess the number of arteries by ultrasound is by identifying the intra-abdominal portion of the umbilical artery alongside the bladder with color Doppler and/or by visualizing the cross-section of a free-floating loop of umbilical cord (**Figure 2**) [20]. In a 1991 study, Nyberg's group concluded that prenatal sonography alone was reliable in detecting any associated anomalies. They also recommended no management modification in cases with no concurrent anomalies [7]. The visualization of that anomaly should prompt a detailed sonographic assessment of the cardiovascular and genitourinary systems [3].

Fetal anomalies most commonly associated with single umbilical artery include several anomalies like ventricular septal defects, hydronephrosis, cleft lip, ventral wall defects, esophageal atresia, spina bifida, hydrocephaly, holoprosencephaly, diaphragmatic hernia, cystic hygromas, and polydactyly or syndactyly. In these cases, fetal echocardiography and karyotype analysis should be considered. Usually, there are no specific fetal abnormalities to be associated with the single umbilical artery. In fact, the single umbilical artery is often found in cases with healthy neonates, with a normal size and development at term. Although, to be sure that the infant has no hidden anomalies, the pediatrician should be notified of its existence to

**Figure 1.** Visualization of the umbilical arteries at the level of the fetal urinary bladder.

fetus, the right umbilical vein disappears by the seventh week of gestation. This condition does not alter the formation of ductus venosus, the distribution of blood to the fetus remaining normal [24]. First-trimester folic acid deficiency, teratogens such as retinoic acid or early obstruction of the left umbilical vein from external pressure or occlusion are considered

Abnormalities of the Umbilical Cord http://dx.doi.org/10.5772/intechopen.72666 349

The ultrasound diagnosis is made in the transverse section of the fetal abdomen. Umbilical vein is abnormally connected to the right portal vein instead to the left portal vein, and fetal gallbladder is located between the umbilical vein and the stomach [26] (**Figures 4** and **5**).

It is associated with congenital anomalies: cardiac anomalies, trisomy 18, abdominal visceral situs inversus, total anomalous pulmonary venous connection, urinary tract malformation like unilateral renal agenesis, umbilical vein varix, skeletal malformations, and others [27].

**Figure 4.** Persistent right umbilical vein: (**a**) Normal section of abdominal circumference and (**b**) section of abdominal

circumference with persistent right umbilical vein view.

etiologic factors [25].

**Figure 3.** SUA at necropsy.

**Figure 2.** Color Doppler visualization of a free-floating loop of umbilical cord.

have a more detailed physical examination [11, 21]. Ultrasound views of the heart described in FMF's recommendations (minimum four-chamber view, outflow tract, and three-vessel view) can detect 66% of the heart malformations associated with single umbilical artery. The undiagnosed ones are minor and have a favorable outcome [22].

Nonisolated SUA requests invasive testing with chromosomal microarray because the risk of syndromes and chromosomal anomalies are substantially increased (**Figure 3**). Isolated SUA with a normal insertion of the cord does not require special precautions during labor. In these cases, the long-term outcome for children is the same as for children born with three vessels in the umbilical cord [23].

#### **2.2. Persistent right umbilical vein**

Unusual persistence of the right umbilical vein with left vein umbilical regression will lead to alteration in the development of embryonic vasculature, knowing that in the normal

**Figure 3.** SUA at necropsy.

have a more detailed physical examination [11, 21]. Ultrasound views of the heart described in FMF's recommendations (minimum four-chamber view, outflow tract, and three-vessel view) can detect 66% of the heart malformations associated with single umbilical artery. The

Nonisolated SUA requests invasive testing with chromosomal microarray because the risk of syndromes and chromosomal anomalies are substantially increased (**Figure 3**). Isolated SUA with a normal insertion of the cord does not require special precautions during labor. In these cases, the long-term outcome for children is the same as for children born with three vessels

Unusual persistence of the right umbilical vein with left vein umbilical regression will lead to alteration in the development of embryonic vasculature, knowing that in the normal

undiagnosed ones are minor and have a favorable outcome [22].

**Figure 2.** Color Doppler visualization of a free-floating loop of umbilical cord.

**Figure 1.** Visualization of the umbilical arteries at the level of the fetal urinary bladder.

348 Congenital Anomalies - From the Embryo to the Neonate

in the umbilical cord [23].

**2.2. Persistent right umbilical vein**

fetus, the right umbilical vein disappears by the seventh week of gestation. This condition does not alter the formation of ductus venosus, the distribution of blood to the fetus remaining normal [24]. First-trimester folic acid deficiency, teratogens such as retinoic acid or early obstruction of the left umbilical vein from external pressure or occlusion are considered etiologic factors [25].

The ultrasound diagnosis is made in the transverse section of the fetal abdomen. Umbilical vein is abnormally connected to the right portal vein instead to the left portal vein, and fetal gallbladder is located between the umbilical vein and the stomach [26] (**Figures 4** and **5**).

It is associated with congenital anomalies: cardiac anomalies, trisomy 18, abdominal visceral situs inversus, total anomalous pulmonary venous connection, urinary tract malformation like unilateral renal agenesis, umbilical vein varix, skeletal malformations, and others [27].

**Figure 4.** Persistent right umbilical vein: (**a**) Normal section of abdominal circumference and (**b**) section of abdominal circumference with persistent right umbilical vein view.

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

Abnormalities of the Umbilical Cord http://dx.doi.org/10.5772/intechopen.72666 351

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

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

is 10-fold higher than in singleton pregnancies [32] (**Figure 6**).

specific recommendations can be made.

**Figure 6.** Velamentous cord insertion.

artery are associated with velamentous insertion [14].

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