**1. Introduction**

Umbilical cord makes stable interconnection between fetal well-being and placenta at the fetomaternal interface level. The prenatal ultrasonographic assessment of the umbilical cord offers the possibility to investigate the morphologic characteristics during fetal life, from early to late gestation.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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 the coiling pattern [2].

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).

Abnormalities of the Umbilical Cord http://dx.doi.org/10.5772/intechopen.72666 347

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

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 signifi-

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

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

incidence of fetal growth restriction and small placental size was found [14].

cant increase in adverse perinatal outcomes [18].

(**Figure 1**) by demonstrating the cord's perivesical course [19].

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 utero as prenatal ultrasound becomes more sophisticated nowadays.

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.
