Cystic Hygroma
A fluid-filled area near the baby's neck
A cystic hygroma is a fluid-filled space at the back or side of the baby's neck.
It starts in the lymph system. This is a group of tiny tubes that moves clear fluid through the body. The tubes did not join as expected, so fluid collected near the neck.
The finding may be seen on ultrasound early in pregnancy.
Risk of a chromosome change
A chromosome is a package of instructions that helps the baby grow and develop.
Aneuploidy means the baby has an extra or missing chromosome.
About 6 out of 10 babies with a cystic hygroma have a chromosome change.
Common causes are Turner syndrome, Down syndrome, trisomy 18, and trisomy 13.
What genetic tests may be offered?
- Genetic counseling to explain the choices.
- CVS or amniocentesis to test the baby's chromosomes.
- A chromosome microarray to look for smaller missing or extra pieces.
- If these tests are normal, testing for Noonan syndrome or other gene changes may be discussed.
Is NIPT enough?
NIPT is a blood screening test. It can estimate the chance of some chromosome problems.
It is not a diagnosis and does not check for every cause of a cystic hygroma.
CVS or amniocentesis can give a more certain answer.
What ultrasound checks are needed?
- An early check of the baby's body may be offered.
- A detailed anatomy scan is done at 18 to 22 weeks.
- A fetal echocardiogram is a special ultrasound of the baby's heart.
- Ultrasound is often repeated about every 4 weeks.
What other problems can occur?
Heart problems are the most common. Other parts of the body can also be affected.
Even when chromosome tests are normal, a major body problem is found in about 1 to 3 out of 10 babies.
Fluid may build up under the skin, in the chest, or in the belly. This is called hydrops.
What is the outlook?
The outlook is different for each baby.
Some cystic hygromas get smaller or go away. Normal genetic tests, normal heart and body scans, and no hydrops are good signs.
A growing hygroma, hydrops, or other problems can raise the chance of pregnancy loss or serious illness after birth.
Next step: Meet with a maternal-fetal medicine doctor and a genetic counselor. They can review the ultrasound, explain testing, and plan follow-up care. Educational use only. This handout does not replace care from your pregnancy doctor. Updated August 6, 2026.
References
- International Society of Ultrasound in Obstetrics and Gynecology. Cystic Hygroma: Patient Information. Updated May 2022.
- Assiri A, Bonin B. Cystic Hygroma. VISUOG, International Society of Ultrasound in Obstetrics and Gynecology. Updated August 2025.
- American College of Obstetricians and Gynecologists. Current ACOG Guidance: Non-Invasive Prenatal Testing. Accessed August 2026.
- Malone FD, et al. First-trimester septated cystic hygroma. Obstet Gynecol. 2005;106:288-294.