MFM Consult: Single umbilical artery: What you need to know -

MFM Consult: Single umbilical artery: What you need to know - - ModernMedicine

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A: The finding of a single umbilical artery (SUA) can be a source of concern for both patients and providers. The normal umbilical cord contains 2 arteries and 1 vein; SUA is the result of atrophy or agenesis of 1 of the arteries. An SUA can usually be detected on cross-section of the umbilical cord during an otherwise routine gray-scale, second-trimester ultrasound exam, usually after 18 weeks' gestation. An SUA can also be detected using color-flow Doppler to examine the umbilical arteries in the pelvis (Figure) even at an earlier gestational age (eg, 14 weeks).¹ The incidence of SUA is 0.25% to 1% of all singleton pregnancies and up to 4.6% of twin gestations.²

An isolated SUA with no other structural or chromosomal abnormalities should be distinguished from an SUA that is present with other abnormalities. The rate of associated fetal structural anomalies when an SUA is detected has been reported to range from 13% to 56%.³ The most common associated anomalies have been noted to occur in the renal, cardiovascular, gastrointestinal, and central nervous systems. Genetic syndromes that may feature an SUA include VATER complex (a group of congenital anomalies consisting of vertebral defects, imperforate anus, tracheoesophageal fistula, and radial and renal dysplasia), Meckel-Gruber, and Zellweger. Teratogenic exposures such as maternal hyperglycemia and phenytoin have also been associated with SUA.

When other abnormalities are present, there is an increased likelihood of chromosomal abnormalities as well as other syndromes. Aneuploidy occurs in about 9% (range, 0%-26%) of fetuses with SUA when it is associated with other anomalies.⁴ Trisomies 21 and 18 have been reported in prenatal case series of SUA, but Turner syndrome, triploidy, and chromosomal deletions and rearrangements have also been reported in babies with SUA.

If there are no other evident fetal abnormalities, how should this patient be further evaluated? Is additional testing indicated if additional fetal abnormalities are identified?

Management of single umbilical artery diagnosed in the second trimester

Once the diagnosis of a SUA has been made, a complete evaluation should be performed. The patient's personal and family histories should be reviewed, including any previous pregnancy complications, medication or teratogen exposure, other children with congenital anomalies, and any genetic disorders in the maternal and paternal families. Any aneuploidy screening (such as first-trimester screen, quadruple screen) that the patient has undergone during the pregnancy should be reviewed. If the patient has not undergone screening and the timing is appropriate, it should be offered.

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