|Antenatal scan of 26 weeks. What would be the likely diagnosis?|
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Findings reveal single umbilical artery (two-vessel cord), umbilical cyst, and clenched fist. These findings are associated with Trisomy 18. Amniocentesis was performed.
The umbilical cord normally contains 2 arteries and a single vein. Occasionally, cords have an absence of one umbilical artery, with the left artery absent more commonly than the right. Single umbilical arteries are associated more commonly with fetal anomalies than normal cords.
Single umbilical arteries are found twice as often in white women than in African American and Japanese women. Diabetes increases the risk significantly. Two-vessel cords are found more frequently in fetuses aborted spontaneously. The male-to-female ratio is 0.85:1.
Single umbilical artery is believed to be caused by atrophy of a previously normal artery, presence of the original artery of the body stalk, or agenesis of one of the umbilical arteries.
Of infants with a single umbilical artery, 20-50% have associated fetal anomalies, including cleft lip, cardiovascular abnormalities (especially ventricular septal defects and conotruncal defects), ventral wall defects, central nervous system defects, esophageal atresia, spina bifida, diaphragmatic hernia, cystic hygroma, hydronephrosis, dysplastic kidneys, polydactyly, syndactyly, and marginal and velamentous insertion of the cord.
Thirty percent have congenital
anomalies, which may include trisomy 13, trisomy 18, and triploidy; trisomy
21 is uncommon