Prenatal diagnosis of umbilical cord aneurysm in a fetus with trisomy 18

Aneurysm of the umbilical cord is an extremely rare vascular anomaly. We re port a case of umbilical cord aneurysm with arteriovenous fistula in a fetu s with trisomy 18. At 34 weeks gestation a fetus with suspected intrauterin e growth restriction and oligohydramnios was referred to our institution. U ltrasound examination was confirmatory and additionally revealed multiple m arkers for trisomy 18. In the umbilical cord an aneurysm was diagnosed char acterized by a cystic lesion with hyperechogenic rim measuring 18 x 18 x 19 mm in diameter. Color flow and spectral Doppler examinations showed a let originating from one of the umbilical arteries entering the cystic lesion w hich appeared to be the diluted umbilical vein. Fetal blood sampling and su bsequent karyotyping revealed trisomy 18 (47, XY. +18). The patient elected to terminate the pregnancy. Pathologic examination of placenta. and umbili cal cord confirmed the prenatal diagnosis of umbilical cord aneurysm and ar teriovenous fistula. Histology, demonstrated it strongly dilated umbilical vein, one moderately dilated artery and a second, apparently normal artery.