Hydrops fetalis is the accumulation of fluid in two or more fetal tissues or organs, such as the lungs, heart, abdomen, or skin, leading to skin swelling, pleural effusion, pericardial effusion, or ascites.
Hydrops fetalis, or fetal hydrops, is typically diagnosed during a prenatal ultrasound exam, and may be caused by a blood-type incompatibility between the pregnant person and the fetus but may also be the result of genetic disorders or structural anomalies of the fetal heart and lungs.
Hydrops fetalis is a very serious condition that is difficult to treat and may result in spontaneous abortion (miscarriage) or death of the newborn soon after delivery.
Common symptoms
The main symptoms of hydrops fetalis include:
- High levels of amniotic fluid;
- A placenta that is larger or thicker than normal;
- Fluid noted in the fetal abdominal cavity (known as ascites);
- Generalized skin edema (swelling), particularly of the head, neck, thorax, and abdomen;
- Pleural effusion (fluid around the lungs), which can affect one or both lungs;
- Pericardial effusion (fluid around the heart);
- Enlargement of the fetal liver, spleen, and heart;
- Rapid or irregular fetal heart rate;
- Decreased fetal movements.
These signs are usually picked up on an ultrasound exam during pregnancy.
After birth, the newborn may present with skin that is pale, yellowish, or blue-tinged; generalized edema (swelling); severe abdominal swelling; breathing problems; decreased muscle tone; dermatitis (skin inflammation); facial anomalies; anemia; enlarged liver; or cardiomyopathy (enlarged heart).
Confirming a diagnosis
The diagnosis of hydrops fetalis is made by an OBGYN on prenatal ultrasound, usually between 18 and 22 weeks of pregnancy.
During this ultrasound the doctor or technician is able to observe signs like an increase in amniotic fluid, thickened placenta, fetal skin edema (swelling), and/or accumulation of fluid in the fetal abdomen, heart, liver, spleen, or lungs.
In order to determine the severity of the condition, your doctor may order a fetal blood test that can be drawn from the fetal blood vessels or the umbilical cord, or an amniocentesis, in which a sample of amniotic fluid is collected to be analyzed in the lab.
Possible causes
The main causes of hydrops fetalis include:
- Blood-type incompatibility between the pregnant person and the fetus;
- Congenital anomalies of the fetal heart or lungs;
- Fanconi anemia;
- Genetic disorders, such as Edwards syndrome, Down syndrome, Turner syndrome, or alpha thalassemia;
- Twin-to-twin transfusion syndrome (in the case of monochorionic twin pregnancies);
- Infections during pregnancy, such as cytomegalovirus (CMV), rubella, herpes, syphilis, toxoplasmosis, and parvovirus B19.
Hydrops fetalis is also linked to pregnancy complications like preeclampsia, diabetes, severe anemia, and mirror syndrome (generalized swelling in the pregnant person and the fetus).
Hydrops fetalis may also develop in seemingly healthy pregnancies without an identifiable cause.
Different types
There are two types of hydrops fetalis that are classified according to their cause:
- Immune hydrops fetalis: occurs due to a blood-type incompatibility between the pregnant person and the fetus, which causes the maternal immune system to attack and destroy the fetal red blood cells. This usually happens when the maternal blood type is negative and the fetal blood type is positive;
- Non-immune hydrops fetalis: the more common type of hydrops fetalis, which is caused by conditions or complications that interfere with microcirculation and functioning of the fetal lymphatic system. These conditions can cause fluid to leak out of the blood vessels and accumulate in the spaces around the cells or result in reduced lympathic return.
The type of hydrops fetalis can be determed by a maternal fetal medicine (MFM) specialist based on the results of diagnostic testing during pregnancy, or by a neonatologist after birth.
Treatment options
When hydrops fetalis is diagnosed during pregnancy, an OBGYN or maternal fetal medicine (MFM) specialist may recommend the use of corticosteroids to help speed up fetal development. Surgery may also be recommended while the fetus is still in the uterus (fetal surgery) to correct problems with the fetal heart or lungs in the event that these organs are affected.
In some cases, early delivery may be recommended, normally via cesarean (c-section).
Babies that survive need treatment right away following delivery, however treatment will depend on the extent to which the baby was affected in uteruo and the severity of the disease, which will depend on the cause of the hydrops.
Blood transfusions may be indicated to treat cases of immune hydrops fetalis or non-immune hydrops fetalis caused by anemia or parvovirus infection.
Can hydrops fetalis be cured?
Prognosis depends on the cause and severity of the condition. Mild cases of hydrops fetalis may resolve with treatment, however more severe cases carry an increased risk of miscarriage and neonatal death.
Possible complications
Complications may arise that vary based on the part of the body affected, with the most severe cases involving accumulation of fluid in the fetal brain, which can affect the development of all fetal organs and systems.
Hydrops fetalis can also affect only one part of the body, such as the lungs, in which case only respiratory complications (breathing problems) would be expected.
Because complications can vary, each case of hydrops fetalis requires a team of specialists who can evaluate the severity of the condition and arrange for the most appropriate treatment.