A cystic hygroma refers to an excess fluid accumulation in the space behind the fetal neck and back.
Usually observed via ultrasound examination in the first trimester, it affects approximately 1 in 100 pregnancies.
Once fetal cystic hygroma has been identified, genetic counseling and testing (chorionic villus sampling or amniocentesis) is highly recommended. About half of these pregnancies will have associated chromosomal abnormalities – such as Down syndrome and Turner syndrome. Subsequent detailed ultrasound examination and fetal echocardiography are recommended.
Ultimately, prognosis will depend on the results of genetic and imaging studies and varies widely.