What is a fetal abdominal cyst?

A fetal abdominal cyst is a bubble of fluid in a balloon-like bag in an unborn baby’s belly.

What are the signs of a fetal abdominal cyst?

The cysts don’t usually cause any problems during the pregnancy. Occasionally, if they grow very large they can put pressure on the baby’s developing lungs or other organs. Big cysts can cause problems such as:

• too much fluid in the womb (uterus)
• fluid build-up in the belly
• blockage of the intestines

What types of abdominal cysts are there?

In a female fetus the commonest type is an ovarian cyst. Ovarian cysts often happen because the unborn baby is exposed to the mother’s hormones. There is nothing the baby’s mother can do to prevent one.

Other common types are:

Enteric duplication cyst: these form when the digestive tract splits as its forming.

Mesenteric cyst: these form in the mesentery. The mesentery attaches to the intestines and carry blood vessels that supply them

Choledochal cysts: these form from the bile duct in or near the liver

Genitourinary cysts: these form on a kidney, a ureter (urine-carrying tube), or the bladder

What causes fetal abdominal cysts?

A fetal abdominal cyst is not a cancer. Most fetal abdominal cysts happen when an accidental slip in the normal growth process makes an extra layer or bubble that fills with fluid. Doctors don’t know why it happens.

How is fetal abdominal cyst diagnosed?

A routine ultrasound of the unborn baby will diagnose a cyst. The fetal medicine specialist will study the cyst’s size, location, contents and movement to try an tell what type of cyst it is. Occasionally they might recommend a MRI to help plan if any treatment and follow up after birth that might be needed.

How are the cysts monitored during pregnancy?

Usually regular ultrasound scans are all that is needed to monitor the cyst before birth and most unborn babies can have a normal vaginal delivery. Occasionally, if the cyst is very large it may twist upon itself (torsion) or cause pressure effects on other organs, in these cases the doctor may recommend surgery to drain or remove the cyst, before or after birth. After birth, paediatricians will continue to monitor the cyst in the baby.