Single Umbilical Artery in Pregnancy and Its Significance

The umbilical cord is a lifeline between you and your baby, carrying essential oxygen and nutrients to support healthy growth. Typically, it has three vessels, two arteries and one vein, but sometimes, one artery may be missing, a condition known as a single umbilical artery (SUA). 

While SUA can be harmless in many cases, it can also indicate other health concerns that deserve attention. This condition occurs in about 0.5 to 6% of single pregnancies and is more common in twins, where the risk is three to four times higher. 

Understanding what single umbilical artery means can help you feel more informed and prepared during your pregnancy. Here’s what you need to know.

Understanding the Types of Single Umbilical Artery

A single umbilical artery can be classified into three types:

• Type 1

The entire length of the cord, from baby to placenta, has only two vessels: one artery and one vein.

• Type 2

There are three vessels near the baby’s end of the cord, but at the placental side, about 2 cm from the placenta’s surface, there are only two vessels. The cause of single umbilical artery Type 2 is anastomosis (a connection or joining between two blood vessels that alters normal blood flow).

Both Type 1 and Type 2 are related to developmental issues with the umbilical cord.

• Type 3

The cord initially has three vessels, but one artery becomes blocked (occluded) along its length. This type is linked to circulatory problems affecting the umbilical cord and baby. Sometimes, it may involve the persistence of the original single allantoic artery of the baby stalk.

Why Does a Single Umbilical Artery Occur?

The exact cause of a single umbilical artery condition is not always clear. In some cases, it happens because one of the arteries in the umbilical cord doesn’t develop fully. In others, an artery that initially formed may close off or degenerate early in pregnancy.

Possible reasons for single umbilical artery include:

• Abnormal development of the umbilical cord, where one artery simply fails to form.
• Vascular changes during pregnancy that cause one artery to become blocked or closed.
• Occasionally, the condition arises because a single artery present during early embryonic development persists instead of dividing into two.

Understanding the cause can be complex, but knowing these possibilities helps in monitoring and managing the pregnancy carefully.

Is SUA a Cause for Concern?

Sometimes, a single umbilical artery is simply an isolated finding, meaning the baby is otherwise developing normally. However, in other cases, SUA may be non-isolated and occur alongside other conditions, including:

• Congenital anomalies, particularly affecting the kidneys, heart, or musculoskeletal system. 

A baby with a single artery has a 6.77 times higher risk of congenital anomalies, with the most common being renal (6.48%), followed by cardiovascular (6.25%) and musculoskeletal issues (5.44%). Some renal malformations may be hidden, such as vesicoureteric reflux grade 2 or higher. It’s important to maintain a low threshold for diagnosing and managing urinary tract infections in these babies.

• Chromosomal abnormalities, with neonates having up to a 15 times higher risk if other issues are present.
• Placental abnormalities, with an increased risk reported (odds ratio 3.63, 95% CI 3.01–4.39).
• Hydramnios (excess amniotic fluid), which has also been reported at a higher incidence in some studies (odds ratio 2.80, 95% CI 1.42–5.49).
• Fetal growth restriction, prematurity, and in rare cases, intrauterine and intrapartum death.

READ: Pregnancy Complications: Umbilical Cord Abnormalities

How Is It Detected?

A single umbilical artery problem is most commonly identified during the second-trimester prenatal ultrasound, which examines the number of vessels in the umbilical cord. Prenatal ultrasound evaluations may also be performed in the third trimester to monitor the condition further.

In some cases, follow-up ultrasounds or Doppler imaging are used to confirm the presence of one umbilical artery and to assess the baby’s blood flow and overall development.

Single Umbilical Artery Treatment

There is no direct treatment for a single umbilical artery condition itself. Instead, careful and regular monitoring is essential to ensure the best possible outcome for both you and your baby. 

If you are diagnosed with SUA or notice any concerning signs such as decreased fetal movement, abnormal ultrasound findings, or issues with fetal growth or amniotic fluid levels, it’s important to contact your doctor immediately. 

Regular prenatal visits and detailed ultrasounds help detect any potential complications early. This ongoing monitoring allows your doctor to manage any issues that arise and provide timely interventions if needed, supporting a healthy pregnancy and delivery.

Conclusion

A single umbilical artery may raise concerns, but many babies with SUA are born completely healthy, especially when it is an isolated finding. With careful monitoring and regular check-ups, most pregnancies progress smoothly. If you ever feel uncertain, don’t hesitate to ask your doctor questions. Staying informed is the best way to feel confident and in control throughout your pregnancy.