© 2017, GENASSIST, Inc.     

By Keith S. Wexler, MBA, Maternal Fetal Medicine, Prenatal Diagnosis and Biotech/Life Sciences Consultant, GENASSIST, Inc.

Paul Wexler, M.D., F.A.C.O.G., Medical Director, GENASSIST, Inc.

Clinical Professor, Department of OB/GYN, University of Colorado Health Sciences Center

Clinical Professor, Division of Genetics/Dept. of Pediatrics, Univ. of Colorado/The Children’s Hospital

We are getting one or two referrals a week for a Single Umbilical Artery (Two Vessel Cord) seen by another healthcare provider on ultrasound in pregnancy.

The incidence of a Single Umbilical Artery (Two Vessel Cord) is approximately 0.2% to 1.6% among fetuses with normal chromosomes and 9% to 11% in fetuses with an abnormal number of chromosomes (aneuploidy).

Single Umbilical Artery is also increased in stillborn fetuses or abortuses. Although malformations and or aneuploidy explain most of the antepartum and neonatal losses, infants with no detected malformations except Single Umbilical Artery also have an increase mortality rate.

Recommendation: A patient with a Single Umbilical Artery (Two Vessel Cord) should consider Maternal Fetal DNA and/or amniocentesis to help confirm or rule-out a chromosomal abnormality.

Isolated Single Umbilical Artery after a thorough ultrasound evaluation may still be associated with congenital malformations, intrauterine growth restriction (IUGR) and stillbirth. The risk for IUGR may be 1.5 times to 2 times the baseline incidence of approximately 10%.

Genitourinary and cardiac malformations are most common. Fetal Echocardiogram after 22 weeks gestation is often recommended since 40-90% of fetuses with an abnormal number of chromosomes (aneuploidy) demonstrate cardiac malformations.

However, in the absence of Fetal Echocardiography, the recognition of a four chamber heart and right (RVOT) and left (LVOT) normal ventricular outflow tracts will lower that risk.

The diagnosis of a Single Umbilical Artery has been reported to have a prenatal detection rate of only 65% to 85% and approximately 10% to 15% of fetuses diagnosed with a Single Umbilical Artery will be found to have a three vessel cord at delivery.

A collaborative study done by Yale and Eastern Virginia Medical School in 1994 suggested the absence of the left umbilical artery was more common and was associated with an increased likelihood of both chromosomal and other malformations. Absence of the right umbilical artery appeared to have a lower incidence.