Hydrops can be divided into two major categories or types: immune hydrops (also called erythroblastosis fetalis) and non-immune hydrops. 

Immune Hydrops (erythroblastosis Fetalis)

This occurs when the mother’s immune system attacks the blood cells of the baby. For example, a mother who has an Rh-negative blood type who is carrying a baby with an Rh-positive blood type may have an immune response that attacks and destroys the Rh-positive blood cells of the baby. 

This leaves the baby anemic or with low blood count. As the baby tries to make more blood cells to replace those being destroyed, organs that help make blood become enlarged and begin to fail. These include the liver, kidneys and adrenal gland. The baby’s heart is also affected because the low blood count causes it to have to work harder and it can eventually fail. 

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. 

Most cases of Rh incompatibility (Rh negative mom and Rh positive baby) will result in a mild to moderate hemolytic (blood) problem. However, in 20-25% of cases, a more severe form develops that leads to hydrops fetalis. 

The incidence of immune hydrops has decreased greatly since the introduction of RhoGAM in the 1960's. RhoGAM is a shot given to the mother during pregnancy to keep her body from attacking her baby’s body.

Non-immune Hydrops 

Non-immune hydrops makes up about 75-90% 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:

• Other conditions causing low blood count in the fetus including fetal bleeding (hemorrhage), problems with fetal blood cell production and genetic disorders that cause the blood cells to be more easily destroyed. These conditions make up about 10-27% of cases)
• Certain infections the mother catches in pregnancy and passes to baby (congenital Infections) such as syphilis, cytomegalovirus, and parvovirus (approximately 8% of cases)
• Genetic syndromes and metabolic disorders (approximately 10% of cases)
• Fetal birth defects that affect the heart function. These include defects that cause push on the heart or make the heart work harder. Fetal tumors or masses, such as diaphragmatic hernia, cystic adenomatoid malformation, sacrococcygeal teratomas, or polycystic kidneys (about 10% of cases)
• Fetal heart conditions or birth defects (approximately 40% of cases) such as problems with the placenta, umbilical cord or the mother's body. In approximately 5-8% of the cases, doctors cannot identify a cause. These are classified as idiopathic cases, meaning the hydrops is the result of an unknown cause.

The incidence of immune hydrops/erythroblastosis fetalis has decreased dramatically since the 1960s due to the introduction of Rh immune globulin or RhoGAM as well as improvements in treatment options. The incidence of non-immune 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 hydrops is the result of an infectious process. The range of incidence is reported at one in 1,500 to 4,000 deliveries. 

Because heart anomalies or disorders are a common cause of non-immune hydrops, we highly recommend a fetal echocardiogram (a specialized ultrasound of the heart) to look for any structural abnormalities or abnormal heart rhythms. Other tests may be performed to look for infections, genetic disorders or other congenital issues that have been linked to the development of hydrops. A genetic counselor may be recommended to assist in this evaluation.

If your doctor believes your baby has hydrops, they will refer you to a perinatologist (a specialist that handles high-risk pregnancies).

Hydrops fetalis is a symptom of a underlying problem with your baby. Hydrops usually will rapidly become fatal for your baby if left untreated. An infant/fetus with hydrops is severely compromised. The earlier in the pregnancy the diagnosis is made, the worse the prognosis is. Some babies with hydrops may even die before they are born.

If your child is diagnosed with immune hydrops, urgent evaluation and possible treatment is necessary to prevent stillbirth or fetal death. The treatment will partly depend upon the gestational age at diagnosis and the determination of underlying cause.

There is a 60-90% 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 your 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 is. 

If your obstetrician suspects a problem with your baby, you will likely be referred to a perinatologist. This doctor will perform a targeted ultrasound to look at all of your baby's anatomy (the body and its systems, such as heart, lungs, abdomen, head, brain, arms, legs) and assess the location and amounts of fluid accumulation. 

The perinatologist will assess you and your baby for:

• The causes hydrops
• The progression of hydrops
• Possible treatment options
• Overall well-being including maternal well-being and baby’s growth and activities.

Other specialists you may see are:

• A neonatologist, a specialized pediatric doctor who will care for your baby after delivery
• A genetic physician or genetic counselor who will be evaluating your family health history for possible inheritable conditions that would cause hydrops
• Any other specialists as necessary to address underlying issues or abnormalities uncovered by the overall workup.

Mirror Syndrome

In up to 50% of pregnancies complicated by hydrops, a condition call mirror syndrome (or Ballentine syndrome) will develop. This condition is thought to be a variant of a pregnancy-related blood pressure disease called preeclampsia and may result in life-threatening maternal hypertension (elevated blood pressures) or seizures. The only treatment for mirror syndrome is immediate delivery of the baby 

Treatment for hydrops depends on the determined cause, if any. Otherwise, the care of a baby born with complications of hydrops is primarily focused on comfort measures, if no therapy or treatment is available. 

When the underlying cause is determined to be complications of low blood counts, one potential therapy is transfusion of blood products to the fetus, just as would be done for an adult with critically low blood. This procedure is called a PUBS (percutaneous umbilical blood sampling). A PUBS involved an amniocentesis where a needle is guided by ultrasound into the umbilical cord of the baby so that the blood can be sampled for testing and new blood may be transfused to restore the blood levels. Blood levels are expressed as hematocrit and the initial procedure goal is a hematocrit of 20-25%. A repeat procedure is likely necessary to achieve a final hematocrit of 45-50% within 48-72 hours. (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 who have not shown improvement before birth should be delivered at a tertiary care center with a level III neonatal intensive care unit capable of extensive evaluation and complex care of the compromised newborn immediately after delivery. Because hydrops of uncertain causes are associated with such poor outcomes, you should expect your team of doctors to have very open and frank conversations with you and your family about options of palliative care versus aggressive resuscitation, prior to delivering your baby. A neonatologist will work with you to develop a plan of care for your baby once they are born. 

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

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 they are in the NICU.

If the treatment leads to a reversal and the hydrops resolves, your 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 themself 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.

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% 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.