A single umbilical artery (SUA) is a variation in the normal structure of the umbilical cord.
🔹 Normal umbilical cord
Has three vessels:
Two arteries: carry deoxygenated blood from the baby to the placenta.
One vein: carries oxygenated blood from the placenta to the baby.
🔹 What happens in SUA
In SUA, one of the two umbilical arteries is missing, so the cord has only one artery and one vein.
🔹 How common it is
Occurs in about 0.5–1% of singleton pregnancies and up to 5% of twin pregnancies.
🔹 Possible Causes
Can result from:
Failure of one artery to form.
Early degeneration of one artery after it forms.
Usually, the exact cause is unknown.
🔹 Types
Isolated SUA (iSUA) – no other abnormalities (most common).
Non-isolated SUA – associated with other structural or chromosomal abnormalities.
🔹 Effects and Risks
1. If isolated (no other abnormalities):
Most babies are born healthy.
Slightly increased risk of:
Low birth weight
Preterm delivery
Small for gestational age (SGA)
2. If associated with other anomalies:
Can be linked with:
Chromosomal abnormalities (e.g., trisomy 13, 18)
Cardiac defects
Renal (kidney) abnormalities
Gastrointestinal or central nervous system anomalies
🔹 Diagnosis
Usually detected on prenatal ultrasound, often during the mid-trimester anatomy scan (18–22 weeks).
The umbilical cord vessels can be visualized using color Doppler imaging.
🔹 Management During Pregnancy
If SUA is found:
Detailed ultrasound to look for other structural abnormalities.
Fetal echocardiography (heart scan) if any suspicion of cardiac defect.
Growth monitoring by serial ultrasounds to ensure the baby is growing well.
Amniocentesis or genetic testing may be offered if other anomalies are present.
🔹 Prognosis
Isolated SUA: Excellent outcome; most babies are completely healthy.
Non-isolated SUA: Prognosis depends on the type and severity of associated anomalies.
