SUA- Single Umbilical Artery

There's nothing like an ultrasound to get your heart racing with anticipation (there's a baby inside!) and at the same time get you worried about every possible complication. What your ultrasound technician observed happens to be the most common irregularity to affect the umbilical cord — the supply-and-waste line that connects you with your baby. Fortunately, most two-vessel cords have a happy ending — and a healthy baby to show for them.

During the anatomy ultrasound, one of the things the sonographer looks for is the presence of three vessels within the umbilical cord: one vein (which carries oxygen and nutrients from you to the baby) and two arteries (which shuttle that waste back to you, to be processed and disposed of by your kidneys). Instead of those three vessels, your baby's cord has only two: one vein and one artery. Two-vessel cord — also known as single umbilical artery (SUA) — occurs in 1 percent of singleton pregnancies and 5 percent of twin and multiple pregnancies. Researchers don't quite know what causes SUA, though they theorize that the second artery disappears at some point during early pregnancy.

Although one artery can certainly perform the job of two and sustain a perfectly healthy pregnancy, your practitioner will likely keep a particularly close eye on your baby's development, and may want to run further tests, including more scans (more pictures — yay!) and possibly even a chromosomal analysis to rule out any genetic abnormalities or other congenital problems. The chances are quite good, however, that your baby will be just fine.

Other factors that may increase your risk:
Advanced maternal age (over 40)
Having 3 or more previous children
Diabetes
Female fetal sex

Anywhere from half to two-thirds of babies born with single artery umbilical cord are born healthy and with no chromosomal or congenital abnormalities.

Of the remaining babies with SUA (single umbilical artery) , some studies suggest that about 25 percent have birth defects, including chromosomal and/or other abnormalities.

These can include trisomy 13 or trisomy 18. However, the most common pregnancy complications that occur in infants with SUA are heart defects, gastrointestinal tract abnormalities and problems with the central nervous system.

The respiratory system, urinary tract, and musculoskeletal system may also be affected. One in five babies affected by SUA will be born with multiple malformations.

Aside from these problems, between 15% and 20% of infants with SUA may suffer from intrauterine growth retardation. Single umbilical artery also has an increased miscarriage rate of 22% associated with it, likely due to the increased abnormalities. Furthermore, there is an association between SUA and low birthweight (<2500g) and early delivery (<37 weeks).

Since ultrasound scans are very good at picking up abnormalities, if you have a normal ultrasound, then it is likely that your baby will be born without any congenital or chromosomal abnormalities. A fetal echocardiogram may also be performed to check the health of your child.

In the presence of an otherwise reassuring prenatal ultrasound, the only other change to antenatal care one might make is a growth scan to make sure the baby is growing at a ‘normal’ rate toward the last month of pregnancy.