Chapter 109
##### KEY POINTS

Key Points

• Single umbilical artery (SUA) is one of the most common malformations found in humans.

• Color Doppler techniques have improved the ability to visualize vessels in the umbilical cord, particularly in a transverse view through the fetal bladder.

• Detailed sonographic evaluation of fetal anatomy is important to determine if SUA is isolated or associated with other anomalies.

• If isolated, fetal echocardiography should be considered, but karyotype is not indicated.

• If associated anomalies are present, fetal karyotype should be obtained, with trisomy 18 being the most commonly associated aneuploidy.

• SUA is associated with increased perinatal mortality, increased chance of IUGR, and slightly increased prematurity.

• If no additional anomalies are detected, postnatal urologic radiographic investigations are not indicated.

• For surviving infants, long-term prognosis is excellent.

##### CONDITION

The normal umbilical cord consists of three vessels—two arteries and one vein (Figure 109-1). Single umbilical artery (SUA) refers to the congenital absence of one of the arteries. The condition was originally described by Vesalius in 1543, Fallopio in 1561, and by Bauhin in 1621 (Persutte and Hobbins 1995). The first prenatal diagnosis of SUA was made in 1980 (Jassani et al., 1980). SUA is one of the most common malformations found in humans.

###### Figure 109-1

Color Doppler study demonstrating the presence of two umbilical arteries and one umbilical vein.

##### INCIDENCE

In prospective studies of liveborn infants, the incidence of SUA varied from 344 in 39,773 (0.9%) to 782 in 372,066 (0.48%) births in the United States National Collaborative Perinatal Project and a Swedish registry, respectively (Froehlich and Fujikura, 1973; Lilja, 1991). The incidence was twofold to threefold higher in a survey of spontaneous abortuses (Byrne and Blanc, 1985). In most studies, the gender distribution is equal. In the National Collaborative Perinatal Project, SUA was noted in 1.2% of white infants and 0.5% of black infants (Froehlich and Fujikura, 1973). SUA occurs three to four times more frequently among twins than among singletons (Heifetz, 1984). Other conditions associated with SUA include maternal diabetes, epilepsy, hypertension, antepartum hemorrhage, polyhydramnios, and oligohydramnios (Persutte and Hobbins, 1995). Maternal age does not affect the incidence of SUA (Prucka et al., 2004).

##### SONOGRAPHIC FINDINGS

The normal umbilical cord contains two arteries and one vein (see Figure 109-1). SUA is easiest to demonstrate in crosssectional images (Figure 109-2) but may also be visualized longitudinally (Figure 109-3). The most reliable technique is to use color Doppler to visualize both umbilical arteries on either side of the dome of the fetal bladder. SUA can be diagnosed in the first trimester (Rembouskos et al., 2003). Fetuses with SUA have an increased diameter ...