My sister had a pregnancy ultrasound and they said the umbilical cord has only one artery. What does this mean?
Q: My sister had a pregnancy ultrasound and they said the umbilical cord has only one artery. What does this mean?
A: Normally, a fetus' heart pumps its blood to the placenta via the umbilical cord's two arteries. In the placenta, oxygen and nutrition from mom's blood are transferred to the fetus's blood and waste from the fetus' blood moves to mom's blood. The oxygenated and nutritionally enhanced fetal blood then flows back through the single umbilical vein to nourish the growing fetus.
Although a normal umbilical cord contains two arteries and one vein, it is not uncommon that a fetus' umbilical cord may have only one artery (called single umbilical artery or SUA). In fact, this occurs in up to 7 percent of all pregnancies and in up to 1 percent of all live births (it is even more common in twins).
SUA can be due to either failure of two arteries to develop or because one of the arteries does not develop normally and then "wastes away."
Although one artery is sufficient to carry the fetus' blood to the placenta, SUA may be a marker for other developmental abnormalities. More so, there is an increased rate of fetal demise when there is only one umbilical artery; in fact, some studies have noted miscarriage and/or fetal demise in up to 20 percent of fetuses with a SUA.
However, pregnancy ultrasound is not a perfect test - it may miss some fetuses with a SUA or it may not visualize both umbilical arteries in all fetuses that have them. One study found an 89 percent positive predictive value of pregnancy ultrasound for SUA, meaning that of all fetuses noted to have SUA from a pregnancy ultrasound, only 89 percent really do have only one umbilical artery.
At this time, there is nothing that can be done to increase the chances of a live birth for a fetus noted to have SUA, although if indicated and desired by the parents an amniocentesis may be considered to evaluate for possible chromosomal abnormalities (trisomy 13 and trisomy 18 are the most common ones associated with SUA).
Babies born with a SUA have a higher rate of having other abnormalities than the general population. Of the 0.5 percent to 1 percent of babies who are born with SUA, about 10 percent to 25 percent have another congenital abnormality; this is much higher than the 2 percent to 3 percent found in babies without SUA.
So, if your baby is born with a SUA, what should be done? The first step is a complete examination to evaluate for other malformations, such as imperforate anus or skeletal abnormalities.
If abnormalities are found on exam, there is not only an increased risk of a chromosomal defect but also of other developmental defects in organs including the kidneys (lack of one or even both kidneys), the heart, the bones (including the VATER syndrome where - among other things - one of the forearm bones does not develop), as well as the digestive system, the brain and other organs.
However, if no abnormalities are found on exam, the baby's risk of having abnormal chromosomes is less than 3 percent and the risk of the baby having organ defects is also much decreased.
Despite this, some experts recommend a screening ultrasound for all babies born with SUA; an ultrasound to look for kidney problems is often recommended, and one study I found advocated an ultrasound of the baby's heart (a cardiac echo) as well.
If there is a SUA noted on a pregnancy ultrasound, and especially if other fetal abnormalities are found - such as kidney or heart problems - an amniocentesis to test for chromosomal abnormalities may be discussed with the parents. Once a baby is born and is noted to have a SUA, a careful physical examination should be performed and a screening ultrasound to look for other organ abnormalities should be considered.
The good news is that over 75 percent of babies born with SUA have normal chromosomes and no other abnormalities.
Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.
MetroWest Daily News