The big scan – something every pregnant parent looks forward to. We know about the umbilical cord, but what is a single artery umbilical cord (SUA)?
Who has been growing for the last 18-20 weeks? Many cannot wait to see a clear profile shot and others are overjoyed to find out if they will be having a boy or a girl. Few think about potential umbilical cord issues.
While great pictures and finding out the sex are what come to mind for the big scan, the purpose of the scan is to check out fetal development and growth. Providers call this scan an anatomy scan.
As a doula, you are likely aware of the importance of the anatomy scan. While it is not a requirement for everyone to have ultrasounds during pregnancy, it is a standard of practice for most providers in the US.
Occasionally, a provider might find a fetal, umbilical, or placental abnormality. One of the possible abnormalities is a single artery umbilical (SUA) cord. Anytime you hear “abnormality” in relation to pregnancy, it can cause worry.
But what is a single artery umbilical cord? Does having an SUA mean your client or their baby are at risk for complications?
What Is A Single Artery Umbilical Cord?
The umbilical cord is the lifeline between you and baby. During typical development, an umbilical cord has three vessels. One vein brings oxygen and nutrients to the baby. Two arteries carry away waste from the baby.
A single artery umbilical cord has only two vessels. It has one vein, and instead of having two arteries it has just one. An SUA is the same as a two-vessel cord. Different sources use different terms.
Around 1% of singleton pregnancies have an SUA, and just under 5% of twin and multiple pregnancies have an SUA. It is the most common umbilical abnormality.
Is An SUA Dangerous For The Baby?
Anytime your client’s hear “abnormality” they are likely to develop concern for the wellbeing of baby. The good news, although an SUA is an abnormality, most cases are isolated and not related to any dangerous conditions for baby.
Occasionally, an SUA can be related to other abnormalities in baby’s cardiovascular, renal, or other systems, or related to a chromosomal issue. For this reason, your client’s provider may recommend further evaluations. Providers rarely suggest invasive testing for isolated SUA.
A more detailed ultrasound to check for any other abnormalities and ongoing growth monitoring is a common course of action. If providers find another abnormality, it might mean an increased risk of health concerns for baby. However, SUA alone is not the cause for concern.
Some studies have found a slight increased risk of Intrauterine Growth Restriction (IUGR), while others have concluded the risk of IUGR among babies with SUA is the same as the general population. If your client’s provider is concerned about IUGR, they will recommend routine growth monitoring.
Some cases of IUGR are attributed to placental function and blood flow, and the presence of an SUA might be a risk factor. However, as mentioned above, there are not studies which confirm an increased risk so it is something to be aware of but not something to expect to occur.
Will SUA Affect Labor And Birth?
Many experiencing SUA can still have a low risk, uncomplicated vaginal birth. Some studies, however, did find an increased risk of c-section due to small for gestational age (perhaps associated with IUGR) and fetal heartrate concerns showing signs of fetal distress.
One thing which is difficult to decipher with these increased risks is whether they are due to the SUA or are they due to managing labor with SUA. If a baby is measuring small for gestational age or experiencing IUGR, your client is more likely to be induced which increases the likelihood of fetal distress and c-section.
With a single artery, it does seem that baby is at an increased risk of fetal distress and thus anything that also increases the risk of fetal distress (e.g., induction of labor, epidural, etc.) could account for more c-sections or complications among babies with SUA due to combining risk factors.
As your client and their maternity care provider monitor their pregnancy, and plan for labor and birth, it is a good idea for them to discuss how to manage these risks. If there is not a medical indication for an induction, augmentation, or epidural, it’s likely planning a spontaneous birth with fetal monitoring could be ideal.
Anytime a client hears something which deviates from expected normal, especially during pregnancy, concerns can run wild. Hearing a baby having a single artery umbilical cord can be scary. The good news is that often, baby will be healthy and labor unaffected.
In the few situations where other conditions are present or where labor does not unfold as planned, discussing options with their maternity care provider before labor can help your client be prepared.