Hydrops fetalis/Erythroblastosis fetalis

What is hydrops fetalis?

Hydrops fetalis is the name of a condition or symptom. It is not a disease in and of itself, but rather a complication of other conditions. Hydrops fetalis is an abnormal collection of fluid in at least two different fetal compartments. These compartments or spaces can be fluid collection in the abdominal cavity (ascites), around the heart (pericardial effusion), and/or lungs (pleural effusion), or generalized edema or swelling of the skin and throughout the body (anasarca), as well as polyhydramnios (excess amniotic fluid) and placental thickening.

Hydrops can be divided into two major categories or types:

  • immune hydrops (erythroblastosis fetalis)
  • non-immune hydrops.

Immune hydrops is a complicated process that takes place between the baby's blood and the mother's blood. If a mother is Rh negative and her baby is Rh positive, the mother's body can react to the Rh positive factor in her baby's blood as if it were a foreign body, such as a virus. The mother's body will make antibodies to attack this foreign body. These antibodies will destroy the baby's blood cells.

This destruction of the baby's blood cells causes an anemia (low blood count) in the fetus or unborn baby. The fetus tries to make more red blood cells but is unable to make enough to replace the ones being destroyed. Then, the liver, spleen, kidney, adrenal glands, and intestine try to help in making red blood cells to try to keep up with the numbers that are being destroyed. The blood cells produced in these other organs are usually immature and are referred to as erythroblasts. This gives us the synonym for immune hydrops, erythroblastosis fetalis. The organs that are trying to produce red blood cells are also unable to keep up with making enough to replace the ones that are being destroyed. As the organs work harder to keep up they become enlarged and distorted. Eventually, hydrops may develop because of problems with the blood flow to and from these organs. Most cases of Rh incompatibility (Rh negative mom and Rh positive baby) will result in a mild to moderate hemolytic (blood) problem. However, in 20 to 25 percent of cases, a more severe form develops. In these cases, the baby develops general swelling of the body, ascites (fluid in the abdomen), pleural effusions (fluid around the lungs) and tachycardia (increased heart rate), the classic picture of hydrops.

The incidence of immune hydrops has decreased greatly since the introduction of RhoGAM in the 1960's.

Non-immune hydrops makes up about 75 to 90 percent of all cases of hydrops seen today. Non-immune hydrops can be the symptom of a number of congenital conditions.

Just a few of the many known causes of hydrops include:

  • Hematologic (blood) problems, such as fetal hemorrhage, disorders in red blood cell production, genetic hemolytic disorders (approximately 10-27 percent of cases)
  • Congenital infections such as syphilis, herpes, cytomegalovirus, parvovirus (approximately 8 percent of cases)
  • Genetic syndromes (approximately 10 percent of cases)
  • Metabolic disorders (falls within the genetic group as these are an inherited disorder)
  • Tumors or masses such as diaphragmatic hernia, cystic adenomatoid malformation, sacrococcygeal teratomas or polycystic kidneys (about 10 percent of cases)
  • Cardiovascular abnormalities which consists of structural problems with the heart, arrhythmias (heart rate too fast or too slow), or vascular (blood vessel) abnormalities (approximately 40 percent of cases)

Also, more rarely, non-immune hydrops can be caused by problems with the placenta, umbilical cord or the mother's body. In approximately 5 to 8 percent of the cases no known cause can be identified. These are classified as idiopathic meaning the hydrops is the result of an unknown cause.

The incidence of immune hydrops or erythroblastosis fetalis has decreased dramatically since the 1960's due to the introduction of Rh immune globulin or RhoGAM as well as improvements in treatment options. The incidence of nonimmune hydrops is hard to calculate because many cases will result in fetal death and/or miscarriage of the baby, and some will get better on their own, especially when it is the result of an infectious process. The range of incidence is reported at 1 in 1,500 to 4,000 deliveries.

Prenatal diagnosis of hydrops fetalis:

Prenatal diagnosis (before birth) of hydrops is accomplished by ultrasound. An abnormal or increased fluid collection is noted in at least two distinct fetal body cavities or spaces. Examples can include the abdomen, around the heart and/or lungs and in the subcutaneous tissue. In most cases there is also a general increase in the amount of amniotic fluid (polyhydramnios) and the placenta is thicker than normal. If fluid accumulation is seen in only one area, the diagnosis of hydrops cannot be made. Instead. an increased amount of fluid is simply noted in that area. To differentiate immune from non-immune hydrops involves a blood test of the mother that looks for antibodies associated with blood-group incompatibility.

Because cardiac (heart) anomalies or disorders are a common cause of non-immune hydrops, a fetal echocardiogram (ultrasound of the heart) is highly recommended to look for any structural abnormalities or abnormal heart rhythms. Other tests may be done looking for infections, genetic disorders or other congenital issues that have been linked to the development of hydrops. Your obstetrician will refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists.

How does hydrops fetalis affect my baby?

Hydrops fetalis is a symptom of a problem with the baby. Immune hydrops will rapidly become fatal for the fetus if left untreated. An infant/fetus with hydrops is severely compromised. The earlier this diagnosis is seen the worse the prognosis. Some of these babies may even die before they are born. When the diagnosis of immune hydrops is made, it needs to be treated as an emergency and immediate arrangements are made for treatment. The treatment will be partly dependent on the gestational age at which the diagnosis was made.

There is a 60 to 90% fetal mortality associated with non-immune hydrops. This mortality rate is dependent on the underlying cause. Many of the underlying congenital anomalies (birth defects) have an extremely high mortality rate in and of themselves. Sometimes, no cause is ever discovered but the perinatologist will be aggressively working to try to find out why the baby has developed hydrops. Some causes can be treated, so the doctor will especially be looking to see if there is a treatable cause. Generally, the earlier in gestation that fetal hydrops is seen, the poorer the prognosis.

If the baby survives to delivery, these babies with hydrops have a distinctive appearance at birth. The babies born with hydrops are very swollen with a large round abdomen due to the fluid collection in the abdominal cavity. Often, these infants will have severe respiratory distress or breathing problems due to a variety of causes. Many have lungs that did not develop completely. This is thought to be a result of limited space in the chest from fluid collecting around the lungs and from a swollen liver and a diaphragm that is pushed upward from the fluid that collected in the abdomen. The polyhydramnios (larger than normal volume of amniotic fluid) may interfere with normal fetal breathing movements also. The smaller than normal lung size results in altered blood flow through the lungs, and higher than normal blood pressure in the lungs. This increased pressure in the lungs limits blood flow through them and limits gas exchange with breathing. The lungs need to rid the blood (and ultimately the body) of carbon dioxide and add oxygen into the blood. Many of these babies have fluid collection around the lungs and/or heart, which complicates already compromised breathing and heart function. Another common complication for these infants is severe low blood sugar (hypoglycemia), which is thought to be the result of altered function of cells in the pancreas. The cause of this altered function is not well understood. Hypoglycemia or low blood sugars put these babies at risk for seizures, apnea and potentially brain injury if not treated quickly. If the underlying cause of the hydrops can be linked to anemia, the baby is at an increased risk of developing hyperbilirubinemia. This problem can become severe very quickly and can potentially cause neurologic injury.

How does hydrops fetalis affect my pregnancy?

If your obstetrician suspects a problem with your baby, you will likely be referred to a perinatologist. These are doctors who handle high-risk pregnancies. The perinatologist will perform a targeted ultrasound to look at all of the baby's anatomy (the body and it's systems such as heart, lungs, abdomen, head/brain, arms, legs) and assess the location and amounts of fluid accumulation. He or she will be assessing you and your baby to look for the cause of the hydrops, follow the progression of fluid accumulation and monitor the well-being of both of you. Other specialists you may see are a neonatologist, who will care for your baby once he or she is born; a geneticist who will be evaluating the family health history; and any other specialist as necessary to treat the birth defect(s) that have been noted on ultrasound.

Hydrops may be complicated by preeclampsia and/or mirror syndrome (involves pregnancy-induced hypertension or high blood pressure with renal/kidney involvement) in up to 50 percent of the cases of non-immune hydrops. With mirror syndrome, symptoms in the mother mirror the symptoms in the fetus and can be life-threatening for her. Mirror syndrome can happen at any time during the pregnancy and can persist even after the baby is born. The only treatment for mirror syndrome is immediate delivery of the baby and/or when possible, treatment of the fetus to resolve the hydrops. Preterm labor can be a complication of polyhydramnios (as well as preeclampsia).

How is fydrops fetalis treated?

Treatment for hydrops is dependent on whether there is a specific diagnosis to treat. Otherwise the treatment is simply supportive or symptom-focused.

Babies with the diagnosis of fetal anemia as the underlying cause of hydrops have good outcomes to fetal therapy. The treatment includes a percutaneous umbilical blood sampling (PUBS) procedure to document the fetal hematocrit and to perform an immediate blood transfusion for the baby. The amount of blood given is calculated using the desired hemotocrit against the actual, the hematocrit of the blood being transfused and the estimated fetal weight. The goal of the initial procedure is a hematocrit to 20 to 25 percent. This procedure is repeated in 48 to 72 hours to bring the hematocrit to 45 to 50 percent. Then, transfusions are done at two- to three-week intervals, with the last one done at 34 to 35 weeks' gestation. These babies should improve before birth.

The treatment protocol for other cases of non-immune hydrops is aimed at the underlying cause. If the underlying cause is known, the benefits and risks of the treatment will be weighed against likelihood of survival. Babies that have not shown improvement before birth should be delivered at a tertiary care center that is able to provide complex resuscitative efforts in the delivery room. Open discussions about palliative care versus aggressive resuscitation can be openly reviewed with you prior to delivery. The plan for care of your baby can be planned with the neonatologist.

For infants without any specific diagnosis, treatment is supportive as we give the baby time to reabsorb all the edema. Often, there are complications like infection and sometimes the baby is unresponsive to the support provided.

The best method for delivery of babies with hydrops is uncertain. To minimize the amount of maternal and fetal trauma, a Caesarean section may be recommended. At delivery, most babies who are being aggressively resuscitated will require endotracheal intubation (the placement of a special tube in the windpipe) for help breathing. Placing the breathing tube can be difficult because of the swelling from the excess fluid. High-frequency ventilation and high airway pressure settings may also be required to provide the baby with enough oxygen. To help the baby breathe, tubes may need to be placed in the chest to help remove fluide from the abdomen and around the lungs.

Special IV lines may be placed. Normally in the umbilical cord there are two arteries and one vein. Umbilical artery catheter is placed in one of the arteries of the umbilical cord. With this special line, fluids can be given, blood pressure can be monitored, and blood can be removed for blood tests. An umbilical venous catheter is placed in the vein of the umbilical cord. With this IV, fluids and medication can be given for a prolonged period of time.

What about surgery?

Some specific anomalies have been treated with fetal surgery (such as congenital cystic adenomatoid malformation and bronchopulmonary sequestration) only if and when the complication of hydrops is seen. You can discuss this option with the perinatologist.

Will I be able to help care for my baby after birth?

Yes. Please ask your baby's nurse about ways to interact with and care for your baby. These babies are typically very ill at birth and will require aggressive treatments. To help in your understanding about what is being done and why ask questions about the treatments and procedures and visit often with your baby.

If you had planned to breastfeed your baby, you can begin to pump and freeze your breast milk while you are still in the hospital. A lactation consultant can assist in answering your questions. Your milk will be frozen and stored in the Neonatal Intensive Care Unit until your baby is ready for it. The NICU has breast pumps and private rooms available to you when you are visiting. You can bring in pictures, small toys, booties and blankets for your baby while he or she is in the NICU.

When can my baby go home?

If the treatment leads to a reversal and the hydrops resolves, the infant may eventually go home. However, for an infant with non-immune hydrops the prognosis is very poor. Your baby must be able to eat enough to maintain and gain weight and breathe effectively by himself or herself before going home. It is important to remember the complication of hydrops has a poor prognosis of survival except for those cases that have a definite cause with established fetal treatment.

What is my baby's long-term prognosis?

Long-term prognosis is guarded. These babies are critically ill even if they do survive to birth. Of the fetuses diagnosed prenatally, only about 20 percent survive to delivery. Of this number, approximately half will survive the neonatal period. Long-term survival for those that make it through the newborn period is based on the underlying cause of the hydrops. The data currently shows an optimistic outlook for those babies who do survive.