What is a cystic hygroma?
A cystic hygroma is a fluid-filled space, usually found at the back of a baby’s neck. It happens when the lymphatic system (which helps drain fluid and forms part of the immune system) does not develop properly. It may be seen on an early pregnancy scan.
It can be seen on an ultrasound scan, sometimes as early as 11–14 weeks. It appears as a clear, fluid-filled area, often behind the baby's head or neck.
Cystic hygromas form when fluid builds up due to problems in the lymphatic system. They can happen by chance or be linked to genetic conditions such as Turner syndrome or Down syndrome.
The outcome depends on whether the cystic hygroma is isolated or associated with other problems. In some cases, it can go away on its own. If linked to a genetic condition, it may affect your baby’s development. Treatment may be needed if the cystic hygroma starts to affect your baby’s breathing. Treatment options postnatally include surgical removal and sclerotherapy (injecting medicine into the cyst, causing it to shrink).
You may be offered more detailed scans and tests (such as, an amniocentesis) to check for genetic conditions. Specialist care may be needed during pregnancy and after birth.
Most of the time a cystic hydroma does not happen again. However, if it is related to a genetic condition, there may be a small chance of recurrence. Genetic counselling is usually offered.