From the Guidelines
A two-vessel umbilical cord detected on a 20-week ultrasound requires additional monitoring due to the potential increased risk of intrauterine growth restriction, preterm birth, and placental issues, but is not necessarily cause for alarm. This finding occurs in about 1% of pregnancies and means the umbilical cord has only one artery and one vein instead of the typical two arteries and one vein. When a two-vessel umbilical cord is detected, a detailed anatomy scan should be performed to look for associated abnormalities, particularly cardiac, renal, and other structural defects, as approximately 20-30% of fetuses with this condition have other anomalies 1.
Key Considerations
- The presence of a two-vessel umbilical cord may be associated with an increased risk of adverse perinatal outcomes, including intrauterine growth restriction and preterm birth 1.
- Management typically includes additional growth scans in the third trimester to monitor fetal growth and well-being.
- Genetic counseling and possibly amniocentesis may be offered depending on other risk factors.
- The single artery must compensate for the missing one, potentially affecting nutrient and oxygen delivery to the developing fetus.
Monitoring and Management
- Serial umbilical artery Doppler assessment should be performed to assess for deterioration, initially every 1-2 weeks 1.
- If the umbilical artery Doppler remains normal, a less frequent interval of umbilical artery Doppler testing may be considered.
- Weekly umbilical artery Doppler evaluation is suggested in pregnancies with severe fetal growth restriction or decreased end-diastolic velocity 1.
- Hospitalization and administration of antenatal corticosteroids may be considered in cases of severe fetal growth restriction or abnormal umbilical artery Doppler indices 1.
From the Research
Significance of a 2-Vessel Umbilical Cord
The detection of a 2-vessel umbilical cord on a 20-week ultrasound is a significant finding that may be associated with adverse pregnancy outcomes. Some key points to consider include:
- A 2-vessel umbilical cord, also known as a single umbilical artery, is a condition where the umbilical cord has only two vessels instead of the usual three 2.
- This condition has been associated with an increased risk of genitourinary defects, as well as other congenital or chromosomal abnormalities 3.
- Studies have shown that fetuses with a 2-vessel umbilical cord are at a higher risk for intrauterine growth restriction, and may also have other structural defects that are not visible on ultrasound examination 2.
- The presence of a 2-vessel umbilical cord may also be associated with intrapartum complications, such as variable decelerations and non-reassuring fetal heart rate patterns 4.
Implications for Patient Counseling and Obstetric Management
The detection of a 2-vessel umbilical cord on ultrasound has significant implications for patient counseling and obstetric management. Some key points to consider include:
- Karyotyping is recommended whenever a 2-vessel cord is seen in association with symmetric intrauterine growth restriction or any other defect 2.
- Fetuses with a 2-vessel cord and any other anomaly on ultrasound often have additional structural defects not seen on scan 2.
- Infants with 2-vessel umbilical cords do not require additional screening for genitourinary defects, unless the imaging or amniocentesis detects a genitourinary abnormality 3.
- Serial ultrasonography and umbilical artery Doppler velocimetry may be used to guide pregnancy management decisions and monitor fetal growth and well-being 5.