Erythroblastosis fetalis is a severe medical condition that most commonly results from incompatibility between certain blood types of a woman who is pregnant and the fetus.

The condition involves a component of blood called Rh factor. Rh factor is an inherited protein, found on the surface of red blood cells. Not everyone has this protein.

If a person has the protein, they are Rh positive. Those who do not have the Rh protein are Rh negative.

If a woman is Rh negative and the fetus is Rh positive, it can lead to Rh incompatibility and potential complications in the pregnancy.

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Problems can sometimes arise if a mother and her unborn child have different blood types.

Erythroblastosis fetalis can occur when different Rh factor blood types mix during pregnancy.

Problems can arise even if small amounts of Rh-positive and Rh-negative blood mix.

Although it is rare for blood between the woman and the fetus to mix during pregnancy, it could happen as a result of:

  • the placenta detaching from the wall of the uterus wall during delivery
  • bleeding during pregnancy
  • manual rotation of a breech baby
  • abortion
  • an ectopic pregnancy
  • a miscarriage
  • a fall, blunt trauma, or invasive prenatal testing
  • prenatal tests, such as an amniocentesis or chorionic villus sampling (CVS)

If Rh-negative blood mixes with Rh-positive blood, an immune response known as Rh sensitization may occur. This means that the person with Rh-negative blood will produce antibodies to fight any future exposure to Rh-positive blood.

The body can also produce antibodies after contamination with a Rh-positive blood from a needle or a blood transfusion.

Once sensitized, the body’s immune system will recognize any future Rh-positive cells as foreign and attack them.

If Rh-positive blood from a fetus gets into the bloodstream of a woman with sensitized Rh-negative blood, the woman’s immune system will attack the invading cells and destroy them.

Erythroblastosis fetalis destroys red blood cells

Destruction of the red blood cells (hemolysis) can be rapid in a fetus. As a result, the fetus will not receive enough oxygen, which may lead to anemia, other illnesses, or even death.

As hemolysis continues, the fetus will rapidly attempt to produce more red blood cells. However, these cells new red blood cells are often immature and are unable to function fully.

Because the body produces red blood cells in the liver and spleen, this overproduction can sometimes cause these organs to enlarge.

When a newborn has this condition, it is known as hemolytic disease of the newborn.

As the immature red blood cells continue to break down, bilirubin, which is a by-product of the breakdown of red blood cells, builds up. The excess amounts of bilirubin circulating in the newborn’s body will lead to jaundice, where the skin and eye whites of the infant turn yellow.

Rh incompatibility is the most common cause of the condition, but other factors can also be responsible, including other cell or blood incompatibilities that produce antibodies.

White infants are more likely to develop the condition than African-American infants.

The risk is also higher in pregnancies where Rh sensitization has already taken place, for example, during a first pregnancy.

It is important to note that having a different blood type to the fetus (ABO incompatibility) is not a cause of erythroblastosis fetalis or hemolytic disease of the newborn, though some other rare blood group differences can occasionally be a cause.

It does not usually affect a first pregnancy, but problems may arise in future pregnancies.

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Ultrasound testing during pregnancy can give a clues about fetal health.

Symptoms of erythroblastosis fetalis during pregnancy may show up during routine testing.

These include:

  • yellow amniotic fluid with traces of bilirubin from an amniocentesis procedure that tests the amniotic fluid
  • an enlarged liver, spleen, or heart
  • a buildup of fluid in the abdomen, lungs, or scalp, detectable through an ultrasound scan during pregnancy

Newborns with the condition may display visible symptoms as well as some that show up on scans, such as:

  • pale skin
  • yellow amniotic fluid, umbilical cord, skin, or eyes, either at birth or within 24 to 36 hours of delivery
  • spleen or liver enlargement

Complications

Complications experienced by the fetus may include:

  • mild-to-severe anemia
  • raised bilirubin levels
  • jaundice
  • severe anemia alongside liver and spleen enlargement

Hydrops fetalis is another severe complication that causes fluid to build up in fetal tissues and organs as a result of heart failure. This is a life-threatening condition.

Complications in a newborn may include:

  • severely high levels of bilirubin, with accompanying jaundice
  • anemia
  • liver enlargement

A buildup of bilirubin in the brain can lead to a complication called kernicterus, leading to seizures, brain damage, deafness, or death.

The first step in diagnosing erythroblastosis fetalis is to determine whether the cause is Rh incompatibility.

A doctor can identify incompatibility using an antibody-screening test in the first trimester. They may repeat the test at 28 weeks of gestation and may also test the Rh factor of the male partner.

Fetal testing may include:

  • an ultrasound
  • amniocentesis, in which the doctor extracts and tests amniotic fluid
  • fetal middle cerebral artery blood flow measurement, to test blood movement in the brain
  • fetal umbilical cord blood testing, to examine the content of blood from the fetus

In the newborn, a doctor may carry out tests to evaluate:

  • blood group and Rh factor
  • red blood cell count
  • antibodies and bilirubin levels

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The newborn may need urgent medical treatment.

Treatment may include a fetal blood transfusion and delivery of the fetus between 32 and 37 weeks gestation.

Treatment options for newborns with the condition include:

  • blood transfusion
  • intravenous (IV) fluids
  • managing breathing problems
  • IV immunoglobulin (IVIG)

The goal of IVIG antibody therapy is to reduce the breakdown of red blood cells and levels of circulating bilirubin.

Sometimes, an exchange transfusion is necessary. This type of transfusion involves replacing small amounts of blood with different blood. The goal is to increase the presence and number of red blood cells and to lower bilirubin levels.

Erythroblastosis fetalis is a preventable condition. A medication called Rh immunoglobulin (Rhig), also known as RhoGAM, can help prevent Rh sensitization.

This medication prevents the pregnant woman from developing Rh-positive antibodies. However, this will not help women who have already undergone Rh sensitization.

Women at risk for Rh sensitization should receive RhoGAM doses at specific times during their pregnancy and after delivery.

These include:

  • at 28 weeks of gestation
  • 72 hours following delivery, if the newborn is Rh-positive
  • within 72 hours of a miscarriage, abortion, or ectopic pregnancy
  • following an invasive prenatal test, such as an amniocentesis or CVS
  • after any vaginal bleeding

If a woman has a pregnancy that extends beyond 40 weeks, the doctor may recommend an additional dose of RhoGAM.

Erythroblastosis fetalis is a potentially dangerous condition that occurs during the development of an infant. The condition occurs when a component of blood called Rh factor is incompatible between the pregnant woman and the fetus.

It can cause jaundice and other, more severe complications, including possible heart failure.

Treatment includes blood transfusion, IV fluids, immunoglobin, and addressing any breathing difficulties.

Giving a pregnant woman Rh immunoglobin can also help prevent the condition by blocking Rh sensitization.