- 1 in 800 pregnancies.
- 1 in 8,000 live births.
- 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.
- Detailed ultrasound examination, including echocardiography.
- Invasive testing for karyotyping and array.
- 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.
- Isolated or part of Turner syndrome: no increased risk of recurrence.
- Part of autosomal recessive syndroms: 25%.