Caused by a blockage in the lymphatic system, cystic hygromas are fluid-filled cysts that most often occur in the neck. Although these growths may occur later in life, they typically develop between 9 and 16 weeks gestation and are often picked up on prenatal ultrasounds, prompting the obstetrician to order genetic testing such as amniocentesis or chorionic villus sampling (CVS). This is because cystic hygromas often occur in conjunction with other serious birth defects, such as the chromosome abnormalities Turner syndrome or Down syndrome.
Babies who have cystic hygromas without chromosome abnormalities generally have a better prognosis, and some cases resolve on their own before birth. Other cases may result in hydrops, which is when an excessive amount of fluid accumulates in the body, leading to fetal death. When the condition is diagnosed prenatally, the baby should be delivered in a hospital that is equipped to deal with neonatal problems. After birth, close observation is required to make sure that the baby's airway does not become obstructed. Treatment consists of surgically removing all or as much of the abnormal tissue as possible.