Hydrops fetalis is severe swelling (edema) in a fetus or a newborn baby, and it is a life-threatening problem. There are two types; immune and nonimmune depending on the cause.

Immune hydrops

The immune version is usually a consequence of Rh incompatibility between the mother and fetus, leading to hemolytic disease of the fetus and newborn (HDFN). If the mother is Rh-negative and is having an Rh-positive baby, the mother’s immune system attacks the unborn baby’s red blood cells. This causes anemia. Hydrops occurs if the developing fetus’s organs are not able to overcome the anemia. Large amounts of fluid will build up in the fetus’s tissues and organs and the heart likely will begin to fail. This type of hydrops is not common today because Rh-negative women are often treated with Rh immunoglobulin to prevent this problem.

Nonimmune hydrops

This is the more common type of hydrops. This type can be caused by many other diseases or complications that may interfere with how a fetus manages fluid. Most of the conditions that can cause nonimmune hydrops are

• Severe anemia,
• Infections present before birth,
• Heart or lung abnormalities,
• Chromosomal abnormalities and birth defects, and
• Liver disease and twin-to-twin transfusion.

During pregnancy, symptoms may include large amounts of amniotic fluid, thickened placenta, and ultrasound of the unborn baby may show enlarged liver, spleen, or heart. It may also show fluid buildup around the fetus’s abdominal organs, heart, or lungs.

Post delivery, symptoms include pale coloration, overall severe swelling, especially in the baby’s abdomen, trouble breathing, enlarged liver and spleen.

How to Diagnose Hydrops Fetalis

Ultrasound: This test uses sound waves to create images of blood vessels, tissues, and organs of the fetus. The healthcare provider will use the ultrasound to look at how a fetus’s internal organs are working and can see how blood flows through different vessels.

The first sign of hydrops fetalis on ultrasound is usually the abnormal accumulation of fluid in fetal compartments. This can include skin edema (thickening of the skin), ascites (fluid in the abdomen), pleural effusion (fluid around the lungs), and pericardial effusion (fluid around the heart). These findings are often accompanied by polyhydramnios (excess amniotic fluid) and placental thickening.

Fetal blood sampling: This is done by placing a needle through the mother’s uterus and into one of the fetus’s blood vessels or the umbilical cord.

Amniocentesis: This test is done by removing some of the amniotic fluid around the fetus for testing.

Assessment of Severity: Once hydrops fetalis is identified, ultrasound is used to assess the severity of the condition. Measurements such as the cardiothoracic ratio, the thickness of the skin edema, and the amount of fluid in each compartment help determine the extent of the disease. Doppler ultrasound is also utilized to evaluate fetal blood flow, particularly in cases of suspected anemia or cardiac issues, providing insights into the fetus’s hemodynamic status.

Determining the Underlying Cause: While ultrasound can easily identify the presence of hydrops fetalis, determining the underlying cause requires a more comprehensive approach. For instance, fetal echocardiography, a specialized form of ultrasound, can assess structural heart defects or cardiac dysfunction. In cases of suspected genetic abnormalities, ultrasound findings may prompt further testing, such as amniocentesis or chorionic villus sampling, to analyze the fetal karyotype.

How is hydrops fetalis treated?

Treatment of hydrops depends on the cause. During pregnancy, hydrops may be treatable only in certain cases. The management of hydrops fetalis is complex and depends largely on the underlying cause, gestational age, and the severity of the condition. Ultrasound continues to play a crucial role in monitoring the fetus and guiding therapeutic interventions.

Fetal Monitoring: For ongoing pregnancies, serial ultrasounds are essential to monitor the progression of hydrops fetalis. Regular assessments of fluid levels, fetal growth, and Doppler studies help guide clinical decisions, such as the timing of delivery. In some cases, ultrasound-guided procedures may be performed to relieve fluid accumulation, such as thoracentesis for pleural effusions or paracentesis for ascites.

Intrauterine Interventions: In certain cases, intrauterine interventions may be considered to improve fetal outcomes. For example, in cases of severe fetal anemia, ultrasound-guided intrauterine transfusions can be performed to deliver blood to the fetus. These procedures are highly specialized and require careful planning and execution.

Delivery Planning: The timing and mode of delivery for a fetus with hydrops fetalis are critical and must be carefully planned based on ultrasound findings. In cases of severe hydrops or fetal compromise, early delivery may be necessary to prevent stillbirth or to provide neonatal care. Ultrasound aids in determining fetal lung maturity and guiding the decision on whether antenatal corticosteroids should be administered to enhance fetal lung development. A mother may need to deliver the baby early.

In a newborn baby, treatment may include:

• Help for breathing problems. This may be with extra oxygen or a breathing machine (ventilator).
• Removing extra fluid from spaces around the lungs, heart, or inside the belly using a needle.
• Fetal blood transfusion in cases with immune hydrops.

The Complications of Hydrops Fetalis

The severe swelling that occurs with hydrops can overwhelm the baby’s organ systems. Approximately 50% of live-born babies with hydrops don’t survive and for those that do, there are risks for other problems. Survival often depends on the cause and treatment.

Key Points on Hydrops Fetalis

• Hydrops fetalis is severe edema in a fetus or newborn baby.
• It is a life-threatening problem.
• Hydrops develops when too much fluid leaves the fetus’s blood and goes into the tissues.
• It is almost always diagnosed during pregnancy or right at birth.
• Treatment of hydrops depends on the cause.
• Approximately 50% of live-born babies with hydrops don’t survive.

Conclusion

Hydrops fetalis is a serious and often fatal condition that requires prompt diagnosis and careful management. Ultrasound is an indispensable tool in both the diagnosis and management of hydrops fetalis, offering detailed insights into the severity of the condition, the underlying causes, and the appropriate course of action. By utilizing ultrasound effectively, healthcare providers can improve the prognosis for affected fetuses, offering the best possible outcomes in challenging situations.

Gerald Walter Mosota is a Diagnostic Medical Sonographer in Mombasa, Kenya.