Skip to Content

What blood type causes miscarriages?


Miscarriage, also known as spontaneous abortion, is unfortunately a relatively common occurrence, affecting up to 1 in 5 recognized pregnancies. Many factors can contribute to miscarriage, including chromosomal abnormalities, hormone issues, uterine abnormalities, infections, and chronic conditions like diabetes and autoimmune diseases. One factor that has been studied in relation to miscarriage risk is the blood type of the mother and father. While no blood type definitively causes miscarriages, some research has found associations between certain blood types and increased miscarriage risk.

Background on Blood Types

Human blood is categorized into different types based on the presence or absence of inherited antigens on the surface of red blood cells. The two most important classifications are the ABO blood group system and the Rh blood group system.

The ABO system has four blood types: A, B, AB, and O. Type A blood has the A antigen, type B has the B antigen, type AB has both A and B, and type O has neither A nor B.

The Rh system consists of Rh positive (Rh+) and Rh negative (Rh-). Those with Rh+ blood have the Rh antigen, while Rh- blood does not have this antigen.

A person’s blood type is determined by the blood types of their parents. The interactions between the parents’ blood types can sometimes increase the risk of complications like miscarriage, especially if the Rh status of the mother and father are incompatible.

The Rh Blood Group System and Miscarriage

The Rh blood group system is one of the most important contributors to miscarriage risk. If a mother is Rh negative and the father is Rh positive, it can lead to Rh incompatibility and associated complications.

Here is an overview of how this happens:

Rh Incompatibility

– If a mother is Rh negative and the father is Rh positive, the fetus may inherit Rh positive blood from the father.

– During pregnancy or delivery, some of the baby’s Rh positive blood cells can mix with the mother’s Rh negative blood. This causes the mother’s immune system to recognize the Rh antigen as foreign and create antibodies against it.

– In future pregnancies with an Rh positive baby, these antibodies can cross the placenta and attack the fetus’ Rh positive blood cells. This leads to hemolytic disease of the newborn.

– Hemolytic disease causes the baby’s red blood cells to break down. This can deprive the baby of oxygen and nutrients and lead to serious complications like miscarriage, stillbirth, or developmental problems after birth.

Risk of Miscarriage

Several studies have found that Rh incompatibility increases the risk of miscarriage:

– A 2005 study found the miscarriage rate was 13.1% in Rh incompatible pregnancies compared to 7.6% in Rh compatible pregnancies.

– A meta-analysis found women with Rh incompatible pregnancies had a 2.7 times higher risk of miscarriage than women without Rh incompatibility.

– The miscarriage risk appears highest during the first trimester before antibodies have developed. One study found 24% of Rh incompatible women miscarried in the first trimester compared to 4.2% of Rh compatible women.

– The risk is increased if the mother already has antibodies against the Rh antigen from a prior pregnancy. One study found a 3.7 times higher miscarriage risk when antibodies were already present.

Therefore, Rh incompatibility, particularly in mothers who already have Rh antibodies, significantly increases the odds of having a miscarriage. However, Rhys negative mothers who receive preventative treatment have miscarriage risks close to the normal population.

Preventing Complications

When an Rh negative mother is expecting an Rh positive baby, injections of anti-D immunoglobulin prevent the mother’s immune system from creating antibodies. This treatment is essential to avoid complications:

– Rh negative mothers should receive anti-D at 28-30 weeks of pregnancy.

– An additional dose is given within 72 hours after delivery if the baby is found to be Rh positive.

– Additional doses may be recommended if there is any potentially sensitizing event during pregnancy like miscarriage, trauma, or invasive tests.

– With preventative treatment, Rh negative women have just a 1-2% higher risk of miscarriage than Rh positive women.

So in summary, Rh incompatibility without preventative treatment significantly increases the risk of miscarriage. But this risk can be minimized by administration of anti-D immunoglobulin.

The ABO Blood Group System and Miscarriage

Unlike the Rh blood types, there is no definitive association between ABO blood types and miscarriage. However, some research has found potential links:

ABO Incompatibility

Similar to Rh incompatibility, maternal-fetal ABO incompatibility occurs when the mother and baby have incompatible ABO blood types. For example, a type A mother and a type B baby.

Some studies have found an increased risk of miscarriage with ABO incompatibility:

– A 2011 study found a 63% higher miscarriage rate with ABO incompatibility.

– A 2010 study found the miscarriage rate was 44.7% with ABO incompatibility versus 11.5% in compatible pregnancies.

– Other studies have found no link between ABO incompatibility and miscarriage risk.

So evidence on the role of ABO incompatibility is still inconclusive and requires further research.

Blood Type and Antibodies

Unlike the Rh system, people do not usually form antibodies against ABO incompatible blood. This means ABO incompatibility is less likely to cause maternal-fetal complications. However, some research suggests certain ABO blood types may have higher natural miscarriage risk:

– A 2019 study found type O mothers had a 60% higher risk of miscarriage than non-O mothers.

– Some studies have found type A mothers may have a higher risk than type O, while others have found no difference between these blood types.

– These potential associations may be related to other immune factors apart from ABO antibodies. For example, type O women may have higher levels of natural killer cells.

Overall, evidence linking ABO blood groups to miscarriage risk is weak. More research is needed on how ABO types could influence antibody levels or other immunologic factors relevant to pregnancy.

Other Blood Group Systems

While the Rh and ABO systems are the most widely known, there are actually over 30 different blood group systems. A couple of the other systems may also be linked to miscarriage risk:

Duffy Blood Group System

– The Duffy group consists of 4 blood types, Fy(a+b+), Fy(a+b-), Fy(a-b+), and Fy(a-b-).

– Fy(a-b-) is the Duffy null blood type, meaning these individuals lack the Duffy antigens on their red blood cells.

– Studies have found the Duffy null type may increase susceptibility to malaria infections during pregnancy, a known cause of miscarriage.

– However, overall evidence directly linking Duffy blood types to miscarriage risk is limited.

Kell Blood Group System

– The Kell group is determined by the presence or absence of the Kell antigen. Most people are Kell positive.

– Kell incompatibility between mother and baby can cause maternal antibodies against fetal blood cells, similar to Rh incompatibility.

– Some studies suggest Kell incompatibility may increase risk of fetal anemia and associated pregnancy complications like miscarriage.

– However, large-scale studies on the role of Kell incompatibility in miscarriage are still needed.

While these other blood group systems may contribute, the associations are not as well-established as the link between Rh incompatibility and miscarriage risk.

Conclusions

In summary:

– Rh incompatibility, particularly in mothers with existing Rh antibodies, significantly increases the risk of first trimester miscarriage. However, preventative treatment helps minimize this risk.

– Evidence for an association between ABO incompatibility or blood type and miscarriage is still inconclusive and requires more research.

– Blood groups like Duffy and Kell may be linked to increased miscarriage risk in some populations, but larger studies are needed.

– No blood type definitively causes miscarriages. Multiple factors are usually involved.

– Genetic testing of both parents can help identify at-risk pregnancies so preventative treatment can be provided early on.

– Any pregnant woman experiencing symptoms like bleeding or cramping should see a doctor right away to rule out threats to the pregnancy like miscarriage.

Frequently Asked Questions

Does having Rh negative blood type cause miscarriage?

No, Rh negative blood type alone does not cause miscarriage. The risk comes from Rh incompatibility between an Rh negative mother and an Rh positive fetus. With proper preventative treatment, Rh negative mothers have just slightly higher miscarriage risks than Rh positive mothers.

Can RhoGAM prevent miscarriage?

Yes, RhoGAM is the brand name for Rh immunoglobulin injections. By preventing Rh negative mothers from forming antibodies against Rh positive fetal blood cells, RhoGAM helps avoid complications like miscarriage, stillbirth, and hemolytic disease of the newborn.

What blood type female gets pregnant easiest?

There is no evidence that any specific blood type among women gets pregnant more easily. The Rh and ABO blood types do not seem to affect fertility or ease of getting pregnant. However, Rh negative women should take precautions to avoid complications during pregnancy.

Can father’s blood type cause miscarriage?

The father’s blood type does not directly cause miscarriage, but it can contribute to problems like Rh incompatibility if it is incompatible with the mother’s blood type. For example, an Rh negative mother with an Rh positive father may face increased miscarriage risks without preventative treatment.

Do O negative mothers have more miscarriages?

A few studies have found that women with O negative blood may have a slightly higher risk of miscarriage compared to other blood types. However, the evidence is still inconclusive, and more research is needed on the mechanisms behind this possible link. In most cases, O negative women can have healthy pregnancies.

Key Takeaways

– Rh incompatibility between an Rh negative mother and Rh positive fetus significantly increases the risk of miscarriage if left untreated. RhIg injections prevent complications.

– ABO incompatibility may increase miscarriage risk in some cases but evidence is still inconclusive.

– Blood groups like Duffy and Kell may contribute to miscarriage risk in some populations.

– No single blood type definitively causes miscarriage – multiple maternal and fetal factors are usually involved.

– Genetic testing can identify at-risk pregnancies. Preventative treatment and close monitoring help minimize risks.