Perinatal Outcomes of Isolated Single Umbilical Artery

Isolated single umbilical artery (iSUA) represents the most common umbilical cord anomaly, occurring in approximately 0.5–1.5 percent of singleton pregnancies. In the absence of co-existing structural or chromosomal abnormalities, iSUA poses a variable risk profile for perinatal complications. Fetuses with iSUA often exhibit adaptive changes in blood flow dynamics, with enlargement of the lone artery and altered resistance indices, yet these adaptations may not fully compensate for the reduced vascular capacity. Clinically, iSUA is associated with an increased likelihood of fetal growth restriction, small-for-gestational-age birthweight, preterm delivery and, in rare cases, intrauterine fetal demise. Early detection by routine anomaly scan allows stratified surveillance throughout gestation, focusing on Doppler assessment of the remaining artery, biometry and cardiac function. A multidisciplinary approach involving obstetricians, sonographers and neonatologists optimises timing and mode of delivery, and informs parental counselling.

Research from Nature Portfolio

Recent studies have refined normative haemodynamic parameters in fetuses with iSUA. In mid-trimester pregnancies, Doppler ultrasonography reveals significantly lower resistance and pulsatility indices in the solitary artery compared with three-vessel cords, with resistance decreasing along the length of the cord toward the placenta. Establishing gestation-specific reference ranges for resistance index and systolic/diastolic ratio enhances the reliability of surveillance protocols. A comprehensive meta-analysis pooling data from multiple centres quantified maternal and neonatal risk factors. It demonstrated that primigravidity and female fetal sex modestly elevate the incidence of iSUA, while affected neonates exhibit lower mean birthweights, higher rates of preterm delivery and increased need for neonatal intensive care. Despite these challenges, perinatal mortality remains comparable to the general population when unaccompanied by additional anomalies, underscoring the value of targeted monitoring.

Perinatal Outcomes of Isolated Single Umbilical Artery publication trend

The graph below shows the total number of articles in perinatal outcomes of isolated single umbilical artery across all publications each year (not limited to Nature Index journals).

Technical terms

Isolated single umbilical artery (iSUA): A cord anomaly in which only one umbilical artery is present without other malformations.

Resistance index (RI): A Doppler metric reflecting downstream vascular resistance, calculated as (peak systolic velocity – end-diastolic velocity) / peak systolic velocity.

Pulsatility index (PI): A Doppler measure of flow variability, given by (peak systolic velocity – end-diastolic velocity) / mean velocity over the cardiac cycle.

Small for gestational age (SGA): A fetal or neonatal weight below the 10th centile for gestational age.

Intrauterine fetal demise (IUFD): Fetal death occurring at or beyond 20 weeks of gestation prior to birth.

References

1. Normal umbilical artery doppler values in 18–22 week old fetuses with single umbilical artery. Scientific Reports (2023).
2. Changes in Artery Diameters and Fetal Growth in Cases of Isolated Single Umbilical Artery. Diagnostics (2023).
3. The Risk Factors and Neonatal outcomes of Isolated Single Umbilical Artery in Singleton Pregnancy: A Meta-analysis. Scientific Reports (2017).
4. Risk of adverse pregnancy outcome in isolated single umbilical artery diagnosed at the mid-trimester anomaly scan: a large Danish retrospective cohort study. The Journal of Maternal-Fetal & Neonatal Medicine (2023).
5. Prenatal Diagnosis of Isolated Single Umbilical Artery: Incidence, Risk Factors and Impact on Pregnancy Outcomes. Medicina (2023).