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Hydrops Fetalis: Cardiac Causes, Diagnosis and Fetal Treatment Options

Posted on by Prof. Dr. İbrahim Cansaran TANIDIR

Hydrops fetalis is a severe and life-threatening clinical condition characterized by fluid accumulation in two or more body cavities in the fetus. Cardiac causes, especially structural heart anomalies and rhythm disorders, are among the most common nonimmune etiologies of hydrops fetalis, and early diagnosis is decisive for prognosis.

The relationship between fetal heart failure and hydrops fetalis is explained through mechanisms of increased central venous pressure and decreased cardiac output. Congenital heart defects, cardiomyopathies, and severe valvular pathologies may impair circulation, leading to pleural effusion (fluid accumulation around the lungs), ascites (fluid accumulation in the abdominal cavity), and subcutaneous edema.

The development of hydrops in fetal arrhythmias is particularly observed in cases of prolonged tachycardia or complete atrioventricular block. Persistent rhythm disorders weaken myocardial functions, leading to heart failure and secondary fluid accumulation; therefore, prenatal rhythm monitoring and timely treatment are critically important.

Diagnosis and management of nonimmune hydrops fetalis include detailed ultrasonography and evaluation of cardiac structure with fetal echocardiography. Early detection of the underlying cardiac pathology contributes to planning intrauterine treatment options and determining postnatal intensive care strategies.

What Is Hydrops Fetalis and What Role Do Cardiac Causes Play in This Condition?

The development of a baby in the womb is a miraculous process that takes place in fluid. However, the fluid balance within the baby’s own body is a completely closed system with its own rules, entirely independent of the surrounding amniotic fluid. In a healthy developmental process, the fluid part of the blood circulating within the baby’s vessels constantly exchanges with the tissues. This is a flawless exchange. The fluid leaking from the vessels into the tissues is collected through the body’s miniature drainage pipes called the lymphatic system and returned to the main bloodstream.

Hydrops fetalis is the complete collapse of this flawless fluid exchange. Instead of remaining inside the vessels, the fluid leaks out uncontrollably. A widespread layer of edema develops under the baby’s skin. At the same time, liters of fluid may accumulate in the abdominal cavity, between the membranes surrounding the lungs, or within the sac surrounding the heart. This accumulation prevents the normal growth of the baby’s organs, restricts movements, and creates a very serious life-threatening risk.

Cardiac causes, meaning heart-related problems, are among the greatest triggers of this fluid leakage. The heart is the main engine that pumps blood throughout the body. When this engine begins to fail, blood cannot move forward comfortably and starts to pool backward into the veins. The pooled blood dramatically increases the pressure within the vessels. As the pressure rises, just like water leaking from a pipe about to burst, the fluid within the blood rapidly escapes into the tissues and body cavities.

How Is Fluid Balance Disrupted in Hydrops Fetalis in an Unborn Baby?

To understand fluid balance in the body, it is necessary to know the microscopic battle inside the blood vessels. Two different forces continuously balance each other within the vessels. The first force is blood pressure. This pressure tries to push fluid through the vessel wall into the tissues. The second force is the pulling power created by proteins in the blood, especially a substance called albumin. These proteins act like sponges, trying to keep the fluid inside the vessel.

When heart failure develops, pumping blood forward becomes difficult. Since the heart cannot eject blood strongly enough, blood begins to accumulate in the major veins trying to return blood to the heart. This accumulation excessively increases the pushing force within the vessels, namely hydrostatic pressure. The proteins acting like sponges can no longer resist this high pressure, and fluid rapidly leaks out.

Moreover, the problem does not end with fluid leaking outward. The lymphatic vessels, which are the body’s drainage system, must empty the excess fluid they collect into the major veins in the neck region. However, because these major veins are already filled to the brim with blood due to heart failure, the lymphatic system cannot release its collected fluid into circulation. Like a sink with blocked drainage pipes, fluid accumulates increasingly within the tissues, eventually leading to the severe and widespread edema known as hydrops fetalis.

Which Structural Heart Diseases Are Included Among the Cardiac Causes in Hydrops Fetalis?

The circulatory system of an unborn baby functions very differently from that of an adult. Since the baby does not yet breathe, the lungs remain collapsed, and oxygen is received from the mother through the umbilical cord. In this special system, the right and left sides of the heart work in parallel rather than sequentially as in adults. However, during fetal development, the right side of the heart undertakes most of the workload. The right heart is responsible for pumping most of the blood coming from the entire body and the cord.

For this reason, structural abnormalities especially affecting the right side of the heart cause fluid balance to deteriorate much more rapidly. Failure of the heart valves to close completely, continuous backward leakage of blood, or obstruction in vascular pathways rapidly trigger hydrops fetalis.

The main structural heart diseases that may lead to this fluid accumulation in the womb include:

  • Ebstein anomaly
  • Pulmonary atresia
  • Tricuspid dysplasia
  • Hypoplastic left heart syndrome
  • Critical aortic stenosis
  • Atrioventricular septal defect

Each of these diseases burdens the heart through different mechanisms. For example, when the valves are not located where they should be, the right atrium may enlarge massively, causing blood to pool in the liver. Blood pooling in the liver is one of the main causes of the rapid accumulation of fluid called ascites in the abdominal cavity. In conditions where the left side of the heart fails to develop, increased pressure on the left side is transmitted to the right side through natural openings within the heart, initiating the same catastrophic scenario.

Why Are Rhythm Disorders Important in the Development of Hydrops Fetalis in Babies?

Another condition as dangerous as structural heart diseases is malfunction of the heart’s electrical system. The heart contracts through signals generated by a tiny electrical station within itself. Under normal conditions, the heart of an unborn baby beats between 120 and 160 times per minute. This rate is ideal for delivering sufficient blood and oxygen to the baby’s tiny body. However, when a short circuit occurs in this electrical system, everything gets completely out of control.

A heart rate rising above 200 beats per minute is extremely exhausting for the baby. The heart begins to beat so rapidly that it does not have enough time to relax and fill with blood between beats. A heart that cannot fill with blood cannot pump sufficient blood to the body no matter how quickly it contracts. In a very short time, this condition tires the heart muscle, enlarges the heart, and triggers sudden heart failure, flooding the baby’s body with fluid.

The exact opposite condition, a very slow heartbeat, is equally dangerous. When the heart rate drops below 60 beats per minute, the heart cannot meet the total blood volume required by the body no matter how strongly it contracts. Antibodies produced by certain maternal rheumatic diseases (such as SLE) may cross the placenta and attack the electrical pathways of the baby’s heart. When these pathways are damaged, the heart rate suddenly decreases, and because the body cannot receive the oxygen it needs, it enters a cycle of heart failure.

Which Tests Are Performed for Cardiac Causes in Suspected Hydrops Fetalis?

When fluid is detected in the baby’s abdomen, lungs, or beneath the skin during routine obstetric examinations, a detailed cardiac examination must be performed without delay. The gold standard for this examination is a method called fetal echocardiography.

Fetal echocardiography is a much more detailed imaging technique than standard ultrasonography, working entirely with sound waves and causing no harm to either the baby or the mother. Ideally, it provides the clearest results when performed between the 18th and 22nd weeks of pregnancy. During this procedure, the specialist physician examines the baby’s tiny heart from every angle as if holding it in their hand. The size of the four heart chambers, the integrity of the walls separating the chambers, the opening and closing movements of the heart valves, and the diameters of the major vessels emerging from the heart are evaluated down to the millimeter level.

Additionally, Doppler technology is used during this examination to measure the direction and velocity of blood flow. Thanks to color Doppler, whether there is backward blood leakage through the heart valves is displayed on the screen like a map. This detailed examination is the only and most reliable way to determine whether the fluid originates from the heart or whether the problem lies entirely in another system.

How Is Hydrops Fetalis Scored with Fetal Echocardiography?

Fetal echocardiography not only captures an image of the heart but also provides a highly critical report card showing how much the heart can withstand this difficult process. This report card is called the Cardiovascular Profile Score. Like the APGAR test performed on newborns, this system mathematically reveals the severity of the condition by scoring the heart health of the unborn baby out of 10.

The main criteria evaluated in this scoring system are:

  • The amount of fluid in the body cavities
  • Blood flow in the umbilical vein
  • The ratio of the heart to the chest cavity
  • The contraction strength of the heart muscle
  • Resistance in the umbilical artery

A perfect score of 10 indicates that the heart is functioning completely healthily. However, a decrease in the score means that alarm bells are ringing. In particular, a score dropping to 7 or below is a highly critical warning sign indicating that the baby’s circulatory system is beginning to fail and urgent intervention is required. Specialists use this scoring not as a one-time test but as a monitoring mechanism repeated regularly to follow the process.

Which Medications Are Given to the Mother for Cardiac Causes in the Treatment of Hydrops Fetalis?

If the cause of hydrops fetalis is a rhythm disorder in the heart, this condition belongs to the group with the highest chance of treatment in the womb. However, since the baby is in the womb, it is not possible to directly give medication or establish intravenous access. To overcome this obstacle, medical science utilizes the permeability of the placenta. Treatment is administered to the mother, and the medications entering the mother’s bloodstream pass through the cord into the baby’s circulation, helping treat the baby’s heart.

The most commonly used cardiac medications during this process include:

  • Digoxin
  • Sotalol
  • Amiodarone
  • Flecainide

The first-choice medications are generally molecules that slow the heart rate while also increasing the strength of contraction. However, because the baby’s body is flooded with fluid (edematous due to hydrops), the transfer of medication from the mother to the baby is much more difficult than normal. Therefore, the mother may need to use quite high doses of medication. During this process, mothers make a great sacrifice for their babies by taking these medications, which may affect their own heart rhythm. For this reason, the mother’s ECG, heart rhythm, and blood values are also regularly monitored throughout treatment.

What Factors Other Than Cardiac Causes Aggravate Hydrops Fetalis?

Sometimes, even when there is no problem in the heart’s own structure or electrical system, non-cardiac causes may burden the heart so severely that the result is still hydrops fetalis. In medicine, this is called high-output heart failure. The heart is forced to work far beyond its limits to deliver oxygen to the tissues and eventually becomes exhausted.

One of the biggest causes of this is severe anemia developing in the baby. When the number of blood cells decreases, the blood must circulate much faster to deliver sufficient oxygen to the body. The heart exceeds its capacity to pump this thin and insufficient blood. Additionally, certain viral infections, especially viruses causing the condition popularly known as fifth disease, may trigger this process by destroying the baby’s blood cells or directly attacking the heart muscle and causing inflammation.

Problems developing within the chest cavity may also prevent the heart from functioning properly by compressing it externally. For example, if the baby’s stomach and intestines move into the chest cavity due to a tear in the diaphragm muscle, the lungs and heart cannot find enough space to grow. A heart subjected to physical pressure from the outside cannot receive enough blood, circulation collapses, and fluid accumulation begins throughout the body.

How Are Delivery and Postnatal Care Managed in Babies Diagnosed with Hydrops Fetalis?

The first minutes of a baby born with hydrops fetalis require one of the most meticulous and well-coordinated operations in the medical world. These babies should be delivered not in an ordinary delivery room but in specialized operating rooms where a fully equipped neonatal intensive care team, pediatric cardiologists, and obstetric specialists are ready. The first few minutes after birth are the most critical period determining whether the baby will survive.

When the baby is born, breathing independently is almost impossible because the lungs and chest cavity are filled with fluid. Standard interventions are ineffective in these babies. The baby must immediately be connected to a ventilator, and the accumulated fluid must be urgently drained.

Emergency interventions performed at birth include:

  • Insertion of a breathing tube into the airway
  • Drainage of fluid from the chest cavity with a needle
  • Establishing intravenous access through the umbilical cord
  • Initiation of blood pressure-raising medications
  • Connection to specialized ventilators

After the fluid in the chest cavity is drained, the lungs finally have the opportunity to expand. However, recovery of the heart takes a little more time. After admission to the intensive care unit, medications strengthening the heart muscle continue to be administered intravenously. During this process, the baby’s fluid balance, kidney function, and nutrition are managed with extreme precision. While diuretic medications are used to eliminate edema from the body, the minerals and proteins required by the body are replaced through intravenous fluids.

Güncellenme Tarihi: 13.10.2026

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