The Fetal Medicine Foundation

Cystic hygroma

Bilateral symmetrical cystic structures located in the occipital-cervical region of the fetal neck. They are differentiated from nuchal edema by the presence of the nuchal ligament (midline septum).
Cystic hygroma is caused by defects in the formation of the neck lymphatics. It is the most common form of lymphangioma (75% are located on the neck, 20% in the axillary region and 5% on the chest wall, abdominal wall and extremities).

Chromosomal abnormalities, mainly Turner syndrome, are found in about 50% of cases.
Genetic syndromes are found in about 40% of cases. The most common are Noonan syndrome (autosomal dominant but >90% are due to de novo mutations; cystic hygromas, hypertelorism, pulmonary stenosis, fetal growth restriction), Multiple-pterygium syndrome (autosomal recessive; cystic hygromas, contractures in all joints, microcephaly and micrognathia), Fryns syndrome (autosomal recessive; anophthalmia, facial cleft, micrognathia, ventriculomegaly, diaphragmatic hernia) and Neu-Laxova syndrome (autosomal recessive; hypertelorism, microcephaly, agenesis of corpus calosum, contractures in the upper and lower limbs, fetal growth restriction).
Hydrops (in addition to cystic hygromas there is generalized edema, ascites, pericardial or pleural effusions) occurs in 60-80% of cases.

Follow-up scans every 4 weeks to assess the evolution of the hygromas and development of hydrops.

Place: hospital with neonatal intensive care and pediatric surgery.
Time: 38 weeks, ealier if hydrops develops.
Method: cesarean section if there is hydrops or large cystic hygromas preventing flexion of the head.

Fetal death: 90%.
In 10% of cases the fetal karyotype is normal, there are no other obvious defects and the hygromas resolve during pregnancy. In these cases the prognosis is good.