What two blood types can't have babies together?

September 27, 2025 •

3 min read

Blood type incompatibility is a real concern in pregnancy, but it is not true that any two blood types can't have babies together. Instead, a specific mismatch involving the Rh factor can cause serious health issues for a baby, especially in subsequent pregnancies.

Quick Summary

No two specific blood types prevent a couple from having a baby, but a mother being Rh-negative and the father being Rh-positive can lead to complications, known as Rh incompatibility. With modern medical care, these risks are well-managed and preventable.

Key Points

No Incompatibility Prevents Conception: It is a myth that certain blood types can't have babies together; the issue is not with conception but with potential complications during pregnancy.
Rh Factor Mismatch is the Primary Concern: The main issue is Rh incompatibility, where an Rh-negative mother carries an Rh-positive baby, which can trigger an immune response.
RhoGAM Prevents Complications: Modern medicine, specifically the use of RhoGAM injections, effectively prevents the mother's immune system from attacking an Rh-positive fetus, protecting future pregnancies.
ABO Incompatibility is Milder: While ABO incompatibility (e.g., Type O mother with a Type A or B baby) can cause mild issues like jaundice, it is less severe than Rh incompatibility and easily managed.
First Pregnancy is Usually Safe: Rh disease is typically a problem in second or later pregnancies because the mother needs to be sensitized first during a previous pregnancy or related event.
Medical Monitoring is Key: Early prenatal care, including blood typing and antibody screening, is essential for identifying and managing any potential blood type incompatibilities.

Understanding the Basics of Blood Types and the Rh Factor

Blood typing is determined by inherited proteins on the surface of red blood cells. The ABO system includes types A, B, AB, and O. The Rh factor, a separate protein, determines if blood is positive (+) or negative (-), with most people being Rh-positive. A baby inherits these factors from both parents, meaning their blood type or Rh factor may differ from their mother's. This can lead to incompatibilities during pregnancy, but these are manageable with prenatal care.

The Key Issue: Rh Factor Incompatibility

Rh factor incompatibility is the primary concern when a mother and baby have mismatched blood types. This occurs when an Rh-negative mother carries an Rh-positive baby. The mother's immune system may react to the baby's Rh-positive blood if it enters her bloodstream, often during delivery or certain procedures.

How Rh Sensitization Affects Pregnancies

First Pregnancy: Problems are uncommon in a first pregnancy as the mother's body is just starting to develop antibodies.
Subsequent Pregnancies: In later pregnancies with an Rh-positive baby, pre-existing antibodies can cross the placenta and attack the baby's red blood cells, potentially causing severe health issues like anemia, jaundice, and organ enlargement.

Other Considerations: ABO Incompatibility

A less severe incompatibility can occur with ABO blood types, typically when a Type O mother carries a baby with Type A, B, or AB blood. A Type O mother naturally has antibodies that can affect the baby, sometimes causing mild jaundice or anemia, which is usually treatable.

The Role of Modern Medicine and Prevention

Rh incompatibility is largely preventable with prenatal care. The key is identifying Rh-negative mothers and administering Rh immunoglobulin (RhIg), such as RhoGAM.

The RhoGAM Treatment Protocol

First dose: Typically given around 28 weeks of pregnancy.
Second dose: Administered within 72 hours of birth if the baby is Rh-positive.
Other situations: May be given after miscarriage, abortion, or procedures where blood mixing could occur.

RhoGAM prevents the mother's immune system from forming antibodies against the baby's Rh-positive blood. Mild issues from ABO incompatibility in newborns, like jaundice, are often treated with phototherapy.

Blood Type Compatibility vs. Infertility

The idea that blood type incompatibility causes infertility is a myth. Blood type does not affect a couple's ability to conceive. The concerns are related to potential complications during pregnancy, which are manageable with medical intervention.

Genetic Inheritance of Blood Types

The Rh factor follows dominant inheritance. The table below shows potential Rh outcomes:


Parents' Rh Status	Potential Baby's Rh Status
Rh-negative mother, Rh-positive father	Baby can be Rh-positive or Rh-negative
Rh-negative mother, Rh-negative father	Baby will be Rh-negative
Rh-positive mother, any father	Baby can be Rh-positive or Rh-negative

This shows why Rh incompatibility is a concern only when an Rh-negative mother is exposed to an Rh-positive baby, highlighting the importance of knowing blood types for family planning.

Conclusion

It's important to clarify that no two blood types prevent a couple from having children. The main issue is Rh incompatibility, which can cause serious problems for an Rh-positive baby carried by an Rh-negative mother. However, the use of RhoGAM has made this condition highly manageable and preventable. Consistent prenatal care, including blood type screening, is crucial for addressing potential incompatibilities and ensuring a healthy pregnancy.

This article is for informational purposes only and is not medical advice. Consult a healthcare professional for diagnosis and treatment.

Frequently Asked Questions

Yes, absolutely. No combination of blood types makes it impossible for a couple to have a baby. The issue is not about infertility but about managing potential Rh incompatibility during pregnancy with modern medical treatments like RhoGAM.

The biggest risk is Rh factor incompatibility. This occurs when an Rh-negative mother has an Rh-positive baby. The mother's immune system can produce antibodies that attack the baby's red blood cells, causing health issues for the baby in subsequent pregnancies.

Usually, Rh incompatibility does not affect the first pregnancy. This is because the mother's immune system is not yet sensitized to the Rh-positive blood. Sensitization most often occurs during delivery when blood may mix, posing a risk to later Rh-positive pregnancies.

RhoGAM is a medication containing Rh immunoglobulin that prevents an Rh-negative mother's immune system from creating antibodies against an Rh-positive baby's blood. It is administered as an injection during pregnancy and after delivery if needed.

ABO incompatibility is a less common and generally milder condition that can occur if a mother with Type O blood has a baby with Type A, B, or AB blood. It can cause mild issues like jaundice, but it is not as severe as untreated Rh disease.

No, blood type has no impact on a couple's ability to conceive. Infertility is a complex issue influenced by many factors, and blood type compatibility is not one of them. The potential complications are limited to the pregnancy itself.

A simple blood test can determine a person's blood type and Rh factor. Early in prenatal care, all pregnant women are tested for their blood type and Rh factor to identify potential issues and plan appropriate treatment if necessary.