Hydrops fetalis is a serious, life-threatening condition in which a fetus or newborn has an abnormal buildup of fluids in the tissue around the lungs, heart, or abdomen, or under the skin. It’s usually a complication of another medical condition that affects the way the body manages fluid.

Hydrops fetalis only occurs in 1 out of every 1,000 births. If you are pregnant and your baby has hydrops fetalis, your doctor may want to induce early labor and delivery of the baby. A baby born with hydrops fetalis may need a blood transfusion and other treatments to remove the excess fluid.

Even with treatment, more than half of babies with hydrops fetalis will die shortly before or after delivery.

There are two kinds of hydrops fetalis: immune and non-immune. The type depends on the cause of the condition.

Non-immune hydrops fetalis

Non-immune hydrops fetalis is now the most common type of hydrops fetalis. It occurs when another condition or disease interferes with the baby’s ability to regulate fluid. Examples of conditions that can interfere with the baby’s fluid management include:

  • severe anemias, including thalassemia
  • fetal bleeding (hemorrhage)
  • heart or lung defects in the baby
  • genetic and metabolic disorders, including Turner syndrome and Gaucher’s disease
  • viral and bacterial infections, such as Chagas disease, parvovirus B19, cytomegalovirus (CMV), toxoplasmosis, syphilis, and herpes
  • vascular malformations
  • tumors

In some cases, the cause of hydrops fetalis isn’t known.

Immune hydrops fetalis

Immune hydrops fetalis usually occurs when the blood types of the mother and the fetus aren’t compatible with each other. This is known as Rh incompatibility. The mother’s immune system may then attack and destroy the baby’s red blood cells. Severe cases of Rh incompatibility can lead to hydrops fetalis.

Immune hydrops fetalis is much less common today since the invention of a medication known as Rh immunoglobulin (RhoGAM). This medication is given to pregnant women at risk of Rh incompatibility to prevent complications.

Pregnant women may experience the following symptoms if the fetus has hydrops fetalis:

  • excess of amniotic fluid (polyhydramnios)
  • thick or abnormally large placenta

The fetus might also have an enlarged spleen, heart, or liver, and fluid surrounding the heart or lungs, observable during an ultrasound.

A baby born with hydrops fetalis may have the following symptoms:

  • pale skin
  • bruising
  • severe swelling (edema), especially in the abdomen
  • enlarged liver and spleen
  • difficulty breathing
  • severe jaundice

Diagnosis of hydrops fetalis is usually made during an ultrasound. A doctor might notice hydrops fetalis on an ultrasound during a routine pregnancy checkup. An ultrasound uses high-frequency sound waves to help capture live images of the inside of the body. You may also be given an ultrasound during pregnancy if you notice the baby is moving less often or you’re experiencing other pregnancy complications, such as high blood pressure.

Other diagnostic tests may be done to help determine the severity or the cause of the condition. These include:

Hydrops fetalis usually can’t be treated during the pregnancy. Occasionally, a doctor may give the baby blood transfusions (intrauterine fetal blood transfusion) to help increase the chances that the baby will survive until birth.

In most cases, a doctor will need to induce early delivery of the baby to give the baby the best chance for survival. This can be done with medications that induce early labor or with an emergency Cesarean section (C-section). Your doctor will discuss these options with you.

Once the baby is born, treatment may involve:

  • using a needle to remove excess fluid from the space around the lungs, heart, or abdomen (thoracentesis)
  • breathing support, such as a breathing machine (ventilator)
  • medications to control heart failure
  • medications to help the kidneys remove excess fluid

For immune hydrops, the baby may receive a direct transfusion of red blood cells that match its blood type. If the hydrops fetalis was caused by another underlying condition, the baby will also receive treatment for that condition. For example, antibiotics are used to treat a syphilis infection.

Women whose babies have hydrops fetalis are at a risk of another condition known as mirror syndrome. Mirror syndrome can result in life-threatening hypertension (high blood pressures) or seizures. If you develop mirror syndrome, you’ll have to deliver your baby immediately.

The outlook for hydrops fetalis depends on the underlying condition, but even with treatment, the survival rate for the baby is low. Only about 20 percent of babies diagnosed with hydrops fetalis before birth will survive to delivery, and of those babies, only half will survive after delivery. The risk of death is highest for babies who are diagnosed very early (less than 24 weeks into pregnancy) or who have structural abnormalities, such as a structural heart defect.

Babies born with hydrops fetalis may also have underdeveloped lungs and be at a higher risk of:

  • heart failure
  • brain damage
  • hypoglycemia
  • seizures