Management of Isolated Single Umbilical Artery

Initial Assessment and Cardiac Evaluation

The American College of Obstetricians and Gynecologists recommends a comprehensive assessment of cardiac anatomy should be performed immediately for a pregnant woman with an isolated single umbilical artery at 18 weeks, as cardiovascular and renal systems are the most commonly affected when single umbilical artery occurs with structural abnormalities 1, 2
A comprehensive cardiac assessment on the anatomy scan is adequate and normal, fetal echocardiography is not routinely warranted for a pregnant woman with an isolated single umbilical artery at 18 weeks 1, 3

The American College of Obstetricians and Gynecologists recommends a third-trimester ultrasound examination to evaluate growth for a pregnant woman with an isolated single umbilical artery at 18 weeks 1, 2, 4
Consider weekly antenatal fetal surveillance beginning at 36 weeks of gestation for fetuses with isolated single umbilical artery, due to increased risks of stillbirth, polyhydramnios, oligohydramnios, placental abruption, cord prolapse, and perinatal mortality 1, 2, 4

The American Academy of Pediatrics should be notified of the prenatal findings of isolated single umbilical artery at the time of delivery, as postnatal examination of infants with prenatal diagnosis of isolated single umbilical artery revealed structural anomalies in up to 7% of fetuses 1, 2, 4

The American College of Obstetricians and Gynecologists recommends that if aneuploidy screening was negative or not previously performed, no additional genetic testing is needed for isolated single umbilical artery, as isolated single umbilical artery shows no increased risk of aneuploidy 5

The American College of Obstetricians and Gynecologists recommends third-trimester ultrasound examination to evaluate fetal growth, as neonates with isolated single umbilical artery have increased rates of growth restriction 5

The American College of Obstetricians and Gynecologists recommends no additional evaluation for aneuploidy for isolated single umbilical artery, regardless of previous aneuploidy screening results, in an 18-week pregnant woman with no other congenital anomalies 6
The Society for Maternal-Fetal Medicine states that diagnostic testing for aneuploidy is not recommended solely for an isolated soft marker following negative screening, in the context of isolated single umbilical artery 7, 6

The American College of Obstetricians and Gynecologists recommends scheduling a third-trimester ultrasound examination, typically at 32-36 weeks, to evaluate fetal growth in pregnancies with isolated single umbilical artery 6
Weekly antenatal fetal surveillance is recommended beginning at 36 0/7 weeks of gestation for pregnancies with isolated single umbilical artery, due to increased risks of stillbirth and other complications 6

The American College of Obstetricians and Gynecologists recommends no genetic counseling or aneuploidy testing for a pregnant woman with an isolated single umbilical artery at 18 weeks, as it shows no increased risk of aneuploidy 8

The American College of Obstetricians and Gynecologists recommends enhanced surveillance in the third trimester, including a third-trimester ultrasound examination at 32-36 weeks to evaluate fetal growth, as neonates with isolated single umbilical artery have increased rates of growth restriction 8
The American College of Obstetricians and Gynecologists recommends weekly antenatal fetal surveillance beginning at 36 0/7 weeks of gestation due to increased risks of stillbirth, polyhydramnios, oligohydramnios, placental abruption, cord prolapse, and perinatal mortality, with a nearly 5-fold increased risk of stillbirth (OR 4.80) 8

The American College of Obstetricians and Gynecologists advises against offering termination of pregnancy for an isolated single umbilical artery, as it is completely inappropriate for an isolated finding with no structural or chromosomal abnormalities 8
The American College of Obstetricians and Gynecologists recommends against ordering unnecessary genetic testing for an isolated single umbilical artery, as it wastes resources and causes unnecessary anxiety when isolated single umbilical artery carries no increased aneuploidy risk 8

Perform an immediate comprehensive cardiac and renal anatomic assessment when isolated single umbilical artery (SUA) is identified on prenatal ultrasound, followed by a third‑trimester growth ultrasound and weekly antenatal surveillance beginning at 36 weeks; no further aneuploidy testing is required regardless of prior screening results. 9, 10
If the routine anatomy scan provides adequate cardiac views that are normal, a dedicated fetal echocardiogram is not routinely indicated. 9, 10

Isolated SUA is defined as the presence of a single umbilical artery without any additional structural or chromosomal abnormalities. 9, 10
Non‑isolated SUA refers to SUA accompanied by one or more structural anomalies; this phenotype carries an aneuploidy risk ranging from 4 % to 50 %. 9, 10

For isolated SUA, additional evaluation for aneuploidy is not recommended, even if earlier screening was low‑risk or declined. 9, 10
Isolated SUA does not confer an increased risk of chromosomal abnormalities. 9, 10

Schedule a third‑trimester ultrasound between 32 and 36 weeks to assess fetal growth; isolated SUA is associated with an adjusted odds ratio of 2.1 for fetal growth restriction (FGR). 9, 10

Initiate weekly antenatal fetal surveillance at 36 weeks gestation because isolated SUA confers an approximately 5‑fold higher risk of stillbirth (OR 4.80; 95 % CI 2.67‑8.62). 9, 10

Notify the pediatric care team of the prenatal SUA finding at delivery; postnatal examination identifies structural anomalies in up to 7 % of infants who were prenatally classified as having isolated SUA. 9, 10
Cardiac defects represent the most common postnatal anomaly in this group. 9

Do not offer pregnancy termination for isolated SUA, as it lacks associated structural or chromosomal abnormalities. 9, 10
Do not order unnecessary genetic testing for isolated SUA, given the absence of increased aneuploidy risk. 9, 10
Do not omit third‑trimester growth assessment; isolated SUA carries a measurable increase in FGR risk. 9, 10
Do not delay weekly antenatal surveillance after 36 weeks, because of the near‑5‑fold rise in stillbirth risk. 9, 10

American Journal of Obstetrics and Gynecology, 2021