Down syndrome in monochorionic twins

Sin IL, Tan TYT
Correspondence: Dr Tony Tan, tan_tony@rafflesmedical.com

ABSTRACT
Down syndrome in monochorionic twins has rarely been reported. We report such a case diagnosed prenatally. Maternal serum screening was performed at 15 weeks for a twin pregnancy which indicated a risk of greater than 1:50 for Down syndrome. The review of early ultrasonography confirmed monochorionic twins. Amniocentesis at 17 weeks’ gestation was performed on one of the twin sacs, which confirmed Down syndrome. A screening scan at 19 weeks’ gestation showed isolated absent nasal bones in both twins. Termination of pregnancy was performed subsequently.

Keywords: amniocentesis, Down syndrome, nasal bone, maternal serum screening, monochorionic twins, twins
Singapore Med J 2009; 50(7): e264-e267