The term hydrops fetalis, or fetal hydrops, refers to a condition in which the fetus shows signs of fluid accumulation in the body.
Hydrops is defined as the presence of abnormal fluid in at least 2 spaces where it is not supposed to be, such as in the abdominal cavity (ascites), chest cavity (pleural effusion), cavity around the heart (pericardial cavity) or in the skin or scalp (referred to as edema).
Fetal anemia accounts for 10% to 27% of hydrops.
Hydrops can be divided into two major categories or types: immune hydrops (also called erythroblastosis fetalis) and non-immune hydrops.
Immune hydrops occurs when the mother’s immune system attacks the blood cells of the baby, leaving 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.
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.
When severe anemia persists, intrauterine transfusion is a potentially life-saving option. 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 percent. A repeat procedure is likely necessary to achieve a final hematocrit of 45-50 percent 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.
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 he or she is born.
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 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 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.
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.