Radiology Teaching Files > Case 56230700

Contributed by: Won Song, Resident, SAMMC, Texas, USA.
History: 22 week old patient: Single intrauterine pregnancy at 22 weeks.   Second trimester fetal ultrasound.

Fig. 1: Grayscale sonographic image of the transverse fetal pelvis.

Fig. 2: Color Doppler transverse images of the fetal pelvis demonstrates a single umbilical artery adjaacent to the urinary bladder and a single umbilical vein.

Fig. 3: Color Doppler and grayscale images of the umbilical in cross section demonstrates 2 vessels within the umbilical cord. The umbilical artery (white arrow) is significantly larger than the umbilical vein.
Findings: Grayscale and color Doppler images of the pelvis demonstrate a single right umbilical artery.  No evidence of a left umibilical artery is noted.  Cross section of the umbilical cord demonstrates a 2 vessel cord.
Diagnosis: Two vessel umbilical cord/Single umbilical artery

A single umbilical artery can be seen in 1-2% of second and third trimester singleton births and up to 3.5% of twin pregnancies.  It can be a normal isolated finding; however, if there are other anomalies present, the rate of aneuploidy increases to 50% (e.g. Trisomy 18 and 13).  No association with trisomy 21 if it is an isolated finding.

In the majority of cases (70%), the left umbilical artery is absent.  Intrauterine growth retardation can be seen in 15% and may be related to poor coiling.  A higher risk of perinatal mortality is also noted.  The SUA is larger than the normal umbilical artery, typically >50% diameter of the umbilical vein.

Other associated anomaliles most commonly occur in the musculoskeletal system (23%), genitourinary (20%), and cardiovascular (19%).  If SUA is not an isolated finding, amniocentesis is indicated due to the higher rate of aneuploidy.

Fused umbilical arteries usually occur within 3 cm of the placenta and is not associated with aneuploidy.  Umbilical vessel thrombosis is rare but is associated with maternal thrombophilia and also has a high fetal mortality.  Excessive Wharton jelly causes an excessive gelatinous stroma and a thick umbilical cord with umbilical vessels displaced from each other.  There is an association with Trisomy 21 and increased risk in the first trimester.


Hagen-Ansert, SL, ed. Textbook of Diagnostic Ultrasonography, St. Louis, Mosby Elsevier, 2006.

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Additional Details:

Case Number: 56230700Last Updated: 2011-10-11
Anatomy: Vascular/Lymphatic   Pathology: Congenital
Modality: USAccess Level: Readable by all users

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