Hydrops fetalis, also known simply as hydrops, occurs when excess fluid builds up in a fetus, causing swelling of tissue. This swelling can occur throughout the fetus’ body, but more commonly occurs in certain areas, typically the abdomen. Hydrops is a very serious condition that causes fetal death in about half of all cases. Fortunately, this condition is rare, occurring in only one out of every 1,000 pregnancies.
Immune vs. Non-immune Hydrops Fetalis
Hydrops is classified according to its cause as immune or non-immune. Immune hydrops fetalis is a consequence of Rh incompatibility. This occurs when there is a specific type of mismatch between the mother’s blood type and the baby’s. If the mother has Rh-negative blood and the baby has Rh-positive blood, the mother’s immune system can attack the red blood cells in the baby’s bloodstream, causing fetal anemia. Because the red blood cells are responsible for carrying oxygen, the baby’s heart must work much harder and pump more blood into the body’s tissues in order to provide an adequate supply of oxygen. This causes edema (swelling) in those tissues, which can overwhelm the baby’s organ systems. Immune hydrops has become very rare thanks to medical advances that enable doctors to easily diagnose and manage Rh incompatibility.
Non-immune hydrops fetalis is more common than the immune variety and springs from a variety of causes, any of which can interfere with fetus’ ability to manage the fluids in its body:
- Anemia caused by something other than Rh incompatibility
- Defects of the heart or respiratory system
- Liver disease
- Certain birth defects
- Congenital infections
- Maternal diabetes
- Turner Syndrome, a rare genetic condition in which a baby girl is missing a chromosome
- Maternal STDs such as syphilis
- Twin to twin transfusion syndrome
- Maternal hypothyroidism
Symptoms and Diagnosis of Hydrops Fetalis
The symptoms of this condition vary according to the cause, but certain signs are consistent regardless. During pregnancy, hydrops can be detected with an ultrasound test. An ultrasound will reveal swelling of the heart, liver, or spleen, as well as fluid buildup in the abdomen. There may also be thickening or enlargement of the placenta, and possibly an excessive amount of amniotic fluid in the uterus (a condition known as polyhydramnios). In some cases the doctor may decide to take a fetal blood sample by putting a needle through the mother’s abdomen.
After the baby is born, the signs of hydrops can include:
- Pale complexion
- Severe swelling, especially in the abdomen
- Breathing difficulty
- Enlarged spleen and liver
- Severe neonatal jaundice
- The appearance of bruises on the skin
Complications of Hydrops Fetalis
Hydrops fetalis can cause miscarriage or stillbirth. The swelling of tissues interferes with organ function, and the demands placed on the heart—which is also subject to this swelling—can cause fetal cardiac arrest. If the baby does survive, he or she is at risk for a type of brain damage called kernicterus, which leads to mental disability and a tendency toward seizures and motor control problems.
Treatment of Hydrops Fetalis
The treatment for hydrops, like the symptoms, depends on the exact cause. Immune hydrops has all but disappeared in the United States since the late 1960s thanks to the RhoGAM shot, which prevents the mother’s immune system from becoming “sensitized” to the fetus’ blood. Changes in the law have also helped—it is now mandatory for physicians to test a pregnant woman to determine her blood type and rule out Rh incompatibility as soon as possible.
Non-immune hydrops is still a problem, however, albeit an uncommon one. Some of the factors that influence treatment decisions include the baby’s age and estimated tolerance for medication, and the severity of the condition. In some cases the doctor may want to induce labor early in order to be able to deal more directly with the problem. Rarely, an in utero blood transfusion may be attempted. Delivery by C-section is also sometimes recommended.
Once the baby is born he or she may be put on a breathing machine, and doctors will use a needle to remove the excess fluid in the spaces in the abdomen and around the lungs. The baby may also be given medication to help its kidneys rid themselves of the excess fluid. In some instances the baby may be given transfusions to flush out of its system any substance that may still be attacking its red blood cells.