Cystic hygroma is caused by malformation or blockage of the lymphatic system that occurs in 1 in 800 pregnancies and 1 in 8,000 live births according to The Fetal Medicine Foundation. A majority ...

Cystic hygroma is often found on a routine 12-week ultrasound, though it can be identified as early as 10 weeks of pregnancy. The condition may appear as excess fluid behind the neck of the fetus.