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.
Rh factor positivity is very common. If a woman who is Rh negative and a father who is Rh positive conceive a child, the fetus may be Rh positive. This can lead to Rh incompatibility and pregnancy complications.
The first pregnancy is not normally affected, but future pregnancies may be compromised.
When can incompatibility cause problems?
Sometimes, the blood supply from the mother mixes with the blood of the fetus during pregnancy. Even if small amounts of the mother's blood are mixed with the blood of the fetus, problems can arise.
Rhesus incompatibility between parents can lead to complications in offspring.
The blood could mix as a result of:
- The placenta becoming detached from the wall of the uterus wall during delivery
- Bleeding during pregnancy
- Manual rotation of a breech baby
- Ectopic pregnancy
- A fall, blunt trauma, or invasive prenatal testing.
Prenatal tests, such as an amniocentesis or chorionic villus sampling, may place a mother with Rh-negative blood at risk for mixing her baby's potentially Rh-positive blood with her own.
If this happens, an immune response known as Rh sensitization may occur in the mother.
This means that the mother will recognize future Rh-positive cells as foreign and her immune system will attack them.
Her body will produce antibodies to fight future exposure to Rh factor, including the blood of her fetus. This can result in the fetus' red blood cells being destroyed.
The antibodies can also be produced after Rh positive blood needle contamination or a blood transfusion with Rh-positive blood.
Erythroblastosis fetalis destroys red blood cells
The result is red blood cell destruction, known as erythroblastosis fetalis during pregnancy.
Destruction of the red blood cells in the fetus can be rapid. As a result, the fetus will not receive enough oxygen. Illness or death may result.
The anemic fetus' body will attempt to produce red blood cells rapidly. This can result in liver and spleen enlargement. In addition, these rapidly-produced red blood cells are often immature. They are not yet able to function properly.
When this condition is present in the newborn, it is called hemolytic disease of the newborn. It can lead to the inability to break down and excrete the red blood cells.
As a result, there will be high levels of bilirubin, a by-product of red blood cell breakdown. The excess circulating bilirubin will lead to jaundice, and the infant will appear yellow in color.
Rh incompatibility is the most common cause of the condition, but it is not the only cause. Other causes include other antigen system incompatibilities.
Caucasian infants are more likely to develop erythroblastosis fetalis than African-American infants. The risk is also higher in pregnancies if Rh sensitization has already taken place during a first pregnancy.
It is important to note that having a different blood type than the fetus is not a cause of erythroblastosis fetalis or hemolytic anemia in the newborn.
During pregnancy, the fetus may display certain symptoms.
- Yellow amniotic fluid with the presence of bilirubin, seen on an amniocentesis
- An enlarged liver, spleen, or heart
- Buildup of fluid in the abdomen, lungs, or scalp, detectable through an ultrasound scan during pregnancy.
Newborns born with the condition may display symptoms such as:
- Pale skin
- Yellow amniotic fluid, umbilical cord, skin, or eyes, either at birth or within 24 to 36 hours following delivery
- Spleen or liver enlargement
- Hydrops fetalis, marked by breathing difficulties and full body fluid buildup.
Complications experienced by the fetus may include:
- Mild to severe anemia
- Raised bilirubin levels
- Jaundice, or yellowing of the skin
- Severe anemia accompanied by liver and spleen enlargement.
Excessive fluid can accumulate in fetal tissues and organs as a result of heart failure. This is referred to as hydrops fetalis, and it is a life-threatening condition. Infants with this condition may be stillborn.
Complications in the newborn may include:
- Severely high levels of bilirubin, with accompanying jaundice
- Liver enlargement.
Excessive buildup of bilirubin in the brain can lead to seizures, brain damage, deafness, or death. This is referred to as kernicterus.
Diagnosis and treatment
The first step in diagnosing erythroblastosis fetalis is to determine if there is Rh incompatibility and maternal antibody titers.
Rhesus factor testing for parents can indicate a potential risk.
This is done by using an antibody screening test in the first trimester. It may be repeated at 28 weeks of gestation. Paternal Rh factor testing may be recommended.
To diagnose the condition, it is important to know if there is Rh incompatibility, specifically during pregnancy.
Testing for the fetus may include ultrasound, amniocentesis, fetal middle cerebral artery blood flow measurement, and fetal umbilical cord blood testing.
In the newborn, blood tests can be carried out to check for hemolytic anemia.
These will include an evaluation of the:
- Blood group and Rh factor
- Red blood cell count
- Antibodies and bilirubin levels.
Treatment of erythroblastosis fetalis during pregnancy 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 fluids
- Management of respiratory difficulties
- Use of intravenous immunoglobulin (IVIG).
The goal of IVIG antibody therapy is to reduce red blood cell breakdown and levels of circulating bilirubin.
Sometimes, an exchange transfusion is necessary. This type of transfusion requires small amounts of the newborn's blood to be removed and replaced by fresh blood. The goal is to increase the presence and number of red blood cells and to lower bilirubin levels.
Rh sensitization can be prevented by giving a medication called Rh immunoglobulin (RhIg), also known as RhoGAM, before a woman becomes sensitized.
This medication prevents the mother from developing antibodies. However, it is not beneficial to women who have already experienced Rh sensitization.
It is recommended that women at risk for Rh sensitization be given RhoGAM at certain times during their pregnancy and after delivery.
- At 28 weeks of gestation
- At 72 hours following delivery, if the newborn is confirmed to be Rh positive
- Within 72 hours of a miscarriage, abortion, or ectopic pregnancy
- Following an invasive prenatal test such as an amniocentesis or chorionic villus sampling
- Following any vaginal bleeding.
If a woman carries beyond 40 weeks of gestation, an additional dose of RhoGAM may be recommended.