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What two blood types cause miscarriage?

Published in Rhesus Disease 3 mins read

The specific blood types that can lead to complications, including miscarriage, occur when a Rhesus negative (RhD negative) mother carries a baby who is Rhesus positive (RhD positive). This condition is known as Rhesus disease or Rh incompatibility.

Understanding Rhesus Disease and Blood Type Incompatibility

Rhesus disease is a condition that can develop during pregnancy when a mother's blood type is RhD negative, and her baby's blood type is RhD positive. It's an immune reaction where the mother's body recognizes the baby's RhD positive red blood cells as foreign.

The Specific Blood Type Combination

Rhesus disease can only happen when there's a particular mix of blood types between the pregnant mother and her unborn baby:

  • Mother's Blood Type: The mother must have a Rhesus negative (RhD negative) blood type.
  • Baby's Blood Type: The baby must have a Rhesus positive (RhD positive) blood type, inherited from the father.

This combination is crucial for the condition to occur. If both mother and baby are RhD negative, or if the mother is RhD positive, Rhesus disease will not be a concern.

Here’s a simple breakdown:

Mother's Blood Type Baby's Blood Type Potential Outcome Risk
RhD Negative RhD Positive Rhesus Disease
RhD Negative RhD Negative No Risk
RhD Positive RhD Positive No Risk
RhD Positive RhD Negative No Risk

How Incompatibility Can Lead to Miscarriage and Other Complications

During pregnancy or birth, small amounts of the baby's RhD positive blood cells can cross into the mother's bloodstream. If the mother is RhD negative, her immune system may respond by producing antibodies against these foreign RhD positive cells.

  • First Pregnancy: Typically, the first pregnancy with an RhD positive baby is not severely affected because the mother's body has not yet produced a significant number of antibodies.
  • Subsequent Pregnancies: In later pregnancies with another RhD positive baby, if the mother has developed antibodies, these antibodies can cross the placenta into the baby's bloodstream. The antibodies then attack the baby's red blood cells, leading to various degrees of hemolytic disease of the fetus and newborn (HDFN).

In severe cases, HDFN can cause the baby to develop:

  • Anemia: Leading to reduced oxygen delivery to organs.
  • Jaundice: Due to the breakdown of red blood cells.
  • Hydrops fetalis: Severe swelling in the baby.
  • Heart failure.

These severe complications can, unfortunately, lead to miscarriage or stillbirth if not effectively managed.

Prevention and Management

Fortunately, Rhesus disease is largely preventable today.

  • Routine Screening: Pregnant women are routinely tested for their blood type and Rh status early in pregnancy. If a mother is RhD negative, her baby's Rh status can be predicted, or regular monitoring can be conducted.
  • Anti-D Immunoglobulin: RhD negative mothers are typically given injections of anti-D immunoglobulin (also known as RhoGAM or Rhophylac). This medicine prevents the mother's immune system from producing antibodies against the baby's RhD positive red blood cells. It's usually given:
    • During the 28th and 34th weeks of pregnancy.
    • After any potential sensitizing events, such as a miscarriage, ectopic pregnancy, abortion, amniocentesis, or any vaginal bleeding during pregnancy.
    • Within 72 hours of delivering an RhD positive baby.

This preventative measure has dramatically reduced the incidence of Rhesus disease and its severe complications, including miscarriage.