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RH Blood Incompatibility: Meaning and Impact in Pregnancy

Medically Approved by Dr. Edward Salko

Table of Contents

photo preparation for blood test by female doctor medical uniform on the table in white bright room nurse pierces the patient's arm vein with needle blank tube

The information in this article is not intended to replace professional medical advice, diagnosis, or treatment. Instead, consult your physician or any licensed healthcare providers if you have questions.

RH blood incompatibility usually doesn’t ring alarm bells unless you’re in a position where you have to exchange a mismatched blood type with another person. One case that best represents this scenario is during pregnancy, wherein the fetus is RH-positive and the mother is not. As a result, immune cells could attack the baby’s blood cells, leading to several medical conditions. Read further to learn how serious RH incompatibility can be. 

What Does RH Mean in Blood Type?

You may have noticed that blood types have positive and negative signs (e.g., O- or AB+). These symbolize the presence or absence of the RH factor.

Rhesus (RH) factor refers to the protein on the surface of erythrocytes or red blood cells. If your blood type is positive, it simply means your RBCs contain the RH factor. This information is particularly significant during pregnancy and blood transfusion, in which matching blood types impact your health and overall survival in life-threatening conditions.

What Is RH Blood Incompatibility? 

Pregnant women with Rh-negative blood may experience RH blood incompatibility or RH disease if they carry a baby with Rh-positive blood. The mismatch is likely due to the father passing the RH factor to the fetus. 

This event leads to RH blood incompatibility sensitization, wherein the mother’s immune system treats the baby’s blood cells as foreign. As a result, antibodies are released to attack and destroy the baby’s red blood cells. 

Pro tip: Knowing your blood type as early in your life as possible can help with many medical situations. Naturally, this includes assessing your compatibility with your spouse. But on top of that, healthcare providers can make quick life-and-death decisions. Learn more about it from our guide on the importance of undergoing a blood type test

RH Incompatibility Prevalence

RH sensitization occurs in one out of 1,000 births, and the prevalence of RH-negative individuals falls under 15%. 

Nevertheless, it’s imperative to check for the likelihood of an incompatibility by knowing your blood type, including the presence of the RH factor. To do this, take a blood test to identify your and your spouse’s ABO and RH blood. Then, consult your doctor regarding the chances of your baby developing RH disease. 


Pregnant mothers may not experience any symptoms of the condition, mainly if sensitization has not occurred. During delivery, the most notable signs of RH factor incompatibility in a newborn include:

  • Jaundice (yellowing of the skin and white area of the eyes)
  • Low muscle tone
  • Lethargy or fatigue
  • Swelling and inflammation
  • Pale coloring due to anemia
  • Rapid heart rate and breathing


An RH-negative mother typically does not experience any adverse health impacts from the incompatibility. However, the fetus may experience complications based on the severity of RH blood disease, characterized by the amount of antibodies produced by the mother. The following are some of the most common effects that often develop without treatment. 

  • Hydrops fetalis

Immune hydrops fetalis refers to fluid build-up or swelling in certain parts of the fetus. It is considered a severe complication of RH blood incompatibility, as extensive swelling or edema can damage the developing organs. 

Fetal hydrops often come after hemolysis or hemolytic anemia, wherein the baby’s red blood cells are destroyed in response to the incompatibility. Antibodies from the mother will target the RH factor protein, which breaks down the RBCs.

Hydrops fetalis is preventable. If you have RH disease during pregnancy, your doctor will prescribe corresponding treatment and management to keep your baby safe from such complications.

  • Liver failure

As soon as the destruction of red blood cells by the antibodies produced by the mother’s immune system, bilirubin in the fetus starts to accumulate. Bilirubin is a yellowish pigment produced as a result of the RBC breakdown. It passes through the liver and can be found in bile.

High bilirubin levels cause jaundice, characterized by yellow skin and eye discoloration. It often signals problems with the liver and the occurrence of hemolytic anemia. 

Newborns with RH disease may experience high bilirubin, leading to liver failure if not treated promptly. Other symptoms of liver problems to watch out for include lack of energy and low muscle tone.  

  • Heart failure 

Severe hemolytic disease in newborns (HDN) brought about by RH disease drastically impacts oxygen and nutrient supply due to low RBCs in the bloodstream. As a result, the baby’s cardiovascular functions become impaired, including the fetal heart rate patterns. This increases the risk of heart failure.

  • Developmental problems

Oxygen is a fundamental requirement for cellular functions. Therefore, a shortage of oxygen, especially in the brain, can have long-term adverse effects. Newborns with mismatched RH factors with their mothers have higher chances of succumbing to brain damage and cognitive problems if the condition is not addressed. 

  • Stillbirth

Carrying a fetus to term can be challenging with RH-negative incompatibility in that the risk for organ failure due to antibody attacks is increased. As a result, without medical intervention and proper management, a stillbirth can be a possible consequence. 

In addition, women with mismatched RH factor to their spouse or partner also have a higher chance of experiencing recurrent stillbirths. This is particularly true after the first pregnancy and delivery experience. 

Testing and Diagnosis 

Rh factor incompatibility can be detected during pregnancy and after birth. Between the two, tracking symptoms when the baby is still in the mother’s womb can help avoid the above mentioned complications. The following are laboratory procedures that aid in diagnosing RH sensitization.

  • Rh-positive antibody test

This test checks whether the mother’s blood contains Rh-positive antibodies. These antibodies indicate that she has become sensitized to Rh-positive blood and may have Rh incompatibility problems.

  • Ultrasound

An ultrasound may be performed to assess the baby for any signs of fluid build-up, which can indicate Rh blood incompatibility.

  • Amniocentesis

An amniocentesis may be recommended to determine the severity of the RH incompatibility and check on the baby’s overall health status. In this procedure, amniotic fluid is extracted from the womb and analyzed to detect proteins and markers of genetic disorders and other conditions.

Pro tip: The presence of RH factor can be detected through a blood test. While you may already know your blood type based on the ABO group, the test may have omitted RH typing. That said, consider taking a standalone blood test for RH that you can order online. 

Treatment Options 

RH incompatibility can be treated with different options designed to minimize the risks and complications associated with the condition. These, of course, vary depending on the severity of the case.

For example, when the mother is sensitized to the Rh factor, closely monitoring the baby’s well-being throughout the pregnancy is imperative. In severe cases, intrauterine blood transfusions may be necessary to maintain the baby’s blood volume and prevent anemia.

Early delivery may be recommended if the baby shows severe anemia or other complications. After birth, special neonatal care, such as exchange transfusions or phototherapy, may be necessary to address complications.

Frequently Asked Questions

photo gorgeous pregnant woman looking on her paperwork

Can you prevent RH incompatibility? 

Naturally, RH disease can be inevitable if the mother-to-be and the father-to-be have a different RH factor in their blood type. However, the complications of RH blood incompatibility can be prevented through treatment and management. Medications like Rho(D) immune globulin can halt antibodies from attacking blood cells with RH proteins. 

Can Rh incompatibility cause anemia? 

Anemia is a possible complication of RH factor incompatibility as red blood cells get destroyed by antibodies. This leads to a low quantity of healthy RBCs, the hallmark of anemia. In this case, the type associated with the condition is hemolytic anemia, which can exacerbate and become severe, leading to the enlargement of the baby’s liver or spleen. 

Can a baby survive Rh disease?

Yes, babies with mild RH factor incompatibility often recover without any long-term complications. During your pregnancy, your healthcare provider will prescribe a treatment that will ensure you can carry the baby to term without any problems. However, suppose the condition is severe, and many blood cells are destroyed. In that case, you may undergo premature delivery so the baby can receive new red blood cells through transfusion.

The Bottom Line

The relationship between blood RH and pregnancy often receives less attention, primarily because the case is relatively rare. However, this should not diminish the severity of the complications of RH diseases, especially if and when the condition develops. To ensure you and your baby are safe, don’t skip the prenatal checkups and testing, as well as the newborn screening after birth.

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