Cystic Hygroma

Cystic hygromas are fluid-filled  sacs that result from a blockage in the lymphatic system. The lymphatic system is a network of vessels that maintains fluids in the blood, as well as transports fats and immune system cells. Cystic hygromas are single or multiple cysts found mostly in the neck region. A cystic hygroma can be present as a birth defect (congenital) or develop at any time during a person’s life. A cystic hygroma in a developing baby can progress to hydrops (an excess amount of fluid in the body) and eventually fetal death. Some cases of congenital cystic hygromas resolve leading to webbed neck, edema (swelling), and a lymphangioma (a benign yellowish-tan tumor on the skin composed of swollen lymph vessels). In other instances the hygroma can progress in size
to become larger than the fetus. 

Cystic hygromas occur in approximately 1% of fetuses between weeks 9 and 16 of pregnancy. 
Genetic syndromes with cystic hygroma as a clinical feature:
• The majority of prenatally diagnosed cystic hygromas are associated with Turner syndrome, a chromosome abnormality in which a female has only one X chromosome instead of two. 
• Chromosome abnormalities such as trisomies 13, 18, and 21 
• Noonan syndrome
Because the risk for a chromosome abnormality approaches 50% when a cystic hygroma is found prenatally, amniocentesis or CVS (chorionic villus sampling) can be performed to diagnose these conditions. :

Prognosis:
In some situations, a cystic hygroma can be present in a healthy baby. If a chromosome abnormality is not found in the fetus, the outcome is generally better than for those who do have a chromosome abnormality. If a cystic hygroma is an isolated finding that resolves around 18-20 weeks gestation and the fetus has normal chromosomes, the outcome is good for 54-80% of these cases. In cases in which an isolated cystic hygroma does not resolve by 20 weeks gestation, 2-9% have a good outcome. Overall, there is generally a poor prognosis associated with the prenatal finding of cystic hygroma. Studies have indicated  that smaller cystic hygromas are more likely to resolve. Oligohydramnios (not enough amniotic fluid) or polyhydramnios (too much amniotic fluid) predicts a poor outcome. Hydrops occurs 22-76% of the time  with a cystic hygroma and is almost always
associated with miscarriage or fetal death.