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 Happens With a Fetal Abdominal Cyst?

A fetus can have one fetal abdominal cyst, or more.

In a female fetus, the most common type of fetal abdominal cyst is an ovarian cyst.

Other cyst types include:

• enteric (en-TARE-ik) duplication cysts: these form when the digestive tract splits as it's forming
• mesenteric (mez-en-TARE-ik) cysts: these form in the mesentery. The mesentery (MEZ-en-tare-ee) attaches to the intestines and contains the blood vessels that supply them.
• genitourinary (jen-ih-toe-YUR-ih-nair-ee) cysts: these form on a kidney, a ureter (urine-carrying tube), or the bladder
• choledochal (KOLE-uh-dok-ul) cysts: these form from the bile ducts in or near the liver

A cyst can cause problems if it:

• blocks the digestive tract
• makes an organ twist until its blood vessels are squeezed shut. This is called torsion (TOR-shun). An organ with blocked blood vessels doesn't get enough oxygen, so part or all of it can die. The type of cyst most at risk for this is an ovarian cyst. Bowel duplication cysts can also lead to twisting of the bowel (called volvulus rather than torsion).

Fetal abdominal cysts usually don't cause problems unless they get very large. A big cyst can put pressure on the baby's developing lungs and other organs. This can cause problems such as:

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

What Are the Signs & Symptoms of a Fetal Abdominal Cyst?

The cysts usually don't cause any symptoms during the pregnancy.

Sometimes doctors can feel the cyst in the baby's belly after birth. Other symptoms of a fetal abdominal cyst after birth include:

• trouble feeding
• crying and fussiness due to pain
• yellow-tinted skin and eyes (jaundice)
• vomiting
• trouble pooping
• trouble peeing

Cysts that are more than 2 inches (5 cm) across may also cause:

• a difficult delivery because of the cyst's size
• trouble breathing if the cyst presses on the diaphragm so the baby's lungs can't expand well

What Causes a Fetal Abdominal Cyst?

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. There is nothing the baby's parents can do to keep a fetal abdominal cyst from forming.

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.

A fetal abdominal cyst is not a cancer.

How Is a Fetal Abdominal Cyst Diagnosed?

A routine ultrasound scan of an unborn baby usually will find a fetal abdominal cyst. An imaging specialist (radiologist) will study the cyst's:

• location
• size
• movement
• contents

By studying the images of the cyst and how it changes with gentle pressure, the radiologist might be able to tell what kind it is. Knowing the type of cyst helps the baby's doctors know what kind of special care, if any, is needed at birth or in the first few weeks of life.

If the screening prenatal ultrasound doesn't show what kind of cyst the baby has, the radiologist may:

• do another ultrasound scan focused on the cyst
• recommend a magnetic resonance imaging (MRI) scan

How Is a Fetal Abdominal Cyst Treated?

Doctors make a plan for treating a fetal abdominal cyst based on:

• its size
• the type of cyst
• how the cyst changes and grows during the pregnancy

The obstetrician (pregnancy specialist) and radiologist will check the cyst with ultrasound scans every few weeks until birth. The doctors work as a team to decide if a C-section delivery is best. But most babies with fetal abdominal cysts are delivered through the vagina.

Surgery to remove a cyst (cystectomy) is sometimes needed to keep it from blocking the digestive tract or to prevent torsion. Pediatric surgeons usually use minimally invasive surgery (laparoscopy) to remove cysts.

Ovarian Cysts

After birth, a baby isn't exposed to the mother's hormones. So an ovarian cyst usually goes away on its own within a few months. The baby's doctor checks ultrasound scans regularly to be sure the cyst goes away.

A large fetal ovarian cyst — one that is more than about 2 inches (5 cm) across — can twist on its stem and squeeze off the blood vessels that carry blood to and from the ovary. To prevent this, doctors usually:

• do an ultrasound scan soon after birth
• recommend surgery to drain or remove the cyst

For a smaller fetal ovarian cyst, the baby's doctor will order an ultrasound scan during the first few weeks after birth to:

• confirm the type of cyst
• guide treatment

If the cyst doesn't go away on its own, the doctor may recommend a cystectomy to remove it.

What Else Should I Know?

Sometimes, treating an ovarian cyst requires removal of the ovary it grew from. The ovary on the other side can release enough hormones and eggs for normal sexual development and pregnancy later in life.