Blood type has no effect on your ability to have and maintain a happy, healthy marriage. There are some concerns about blood type compatibility if you’re planning to have biological children with your partner, but there are options during pregnancy that can help counteract these risks.

It’s a good idea to know your partner’s blood type in the event of an emergency, however. And, depending on your and your partner’s blood type, you may even be able to donate blood to them in an emergency.

Read on to learn more about blood type, and how it may affect your marriage.

Everybody has a blood type. There are four major blood groups:

  • A
  • B
  • O
  • AB

These groups differ primarily on the presence or absence of antigens that can stimulate an immune response.

In addition to these four groups, a protein called Rh factor that may be either present (+) or absent (-) within each group. This further defines blood groups into eight common types:

  • A+
  • A-
  • B+
  • B-
  • O+
  • O-
  • AB+
  • AB-

Your blood type is something you inherit, so it’s predetermined at birth. You cannot change your blood type later in life.

Compatibility in blood group is only a concern for couples if a pregnancy is involved where both partners are the biological parents. That’s because of RH factor.

Rh factor is an inherited protein, so being Rh negative (-) or Rh positive (+) is determined by your parents. The most common type is Rh positive.

Being Rh positive or negative typically does not affect your health, but it could affect your pregnancy.

Rh factor and pregnancy

Rh factor can be a concern if the biological mother is Rh- and the baby is Rh+. Blood cells from an Rh+ baby crossing its Rh- mother’s bloodstream might trigger an immune response. The mother’s body might form antibodies to attack the baby’s Rh+ red blood cells.

At your first prenatal visit, your doctor will suggest a blood type and Rh factor screening. If you are Rh-, your doctor will test your blood again later in your pregnancy to see if you have formed antibodies against Rh factor. That would indicate that your baby is Rh+.

If your doctor identifies a potential for Rh incompatibility, your pregnancy will be monitored closely for any related issues and may need extra care.

Although your blood and your baby’s blood typically do not mix during pregnancy, a minimal amount of your baby’s blood and your blood could come in contact with each other during delivery. If there’s an Rh incompatibility and this happens, your body might produce Rh antibodies against Rh factor.

These antibodies will not cause problems to an Rh+ baby during the first pregnancy. But they can cause issues if you have a subsequent pregnancy and are carrying another child that is Rh+.

If there was an Rh incompatibility in a first pregnancy, and there’s an Rh incompatibility in second and other future pregnancies, these maternal antibodies can damage the baby’s red blood cells. If this occurs, your baby might need a red blood cell transfusion either during your pregnancy or immediately after delivery.

How is Rh incompatibility treated?

If Rh incompatibility has been diagnosed, your doctor will most likely recommend Rh immune globulin (RhoGAM) in your seventh month of pregnancy, and then again within 72 hours after delivery if your baby’s blood type is confirmed as Rh positive upon delivery.

Rh immune globulin contains Rh IgG antibody, so your body does not react to your baby’s Rh positive cells as if they were a foreign substance, and your body will not produce its own Rh antibodies.

Compatible blood types could be useful if you or your partner need a blood transfusion. People without compatible blood types cannot donate blood to each other. A transfusion of the wrong type of blood product can result in a potentially fatal toxic reaction.

Being able to supply needed blood for a partner with a medical issue might not be a deal breaker for most couples, but it could be a nice perk in the event of an emergency.

According to the American Red Cross:

  • If you have type AB+ blood, you are a universal recipient and can receive red blood cells from all donors.
  • If you have type O- blood, you are a universal donor and can donate red blood cells to anyone.
  • If you have type A blood, you can receive type A or type O red blood cells.
  • If you have type B blood, you can receive type B or type O red blood cells.

Rh+ or Rh- blood can be given to those who are Rh+, but if you are Rh-, you can only receive Rh- blood.

So, if you want to be in a position to donate blood to your spouse, make sure you and your future spouse have compatible blood types.

How common are different blood types?

Depending on your blood type, it might be easier or more difficult to find a potential partner with a compatible blood type. According to the Stanford School of Medicine, in the United States:

  • People with the blood type O+ represent about 37.4% of the adult population.
  • People with the blood type O- represent about 6.6% of the adult population.
  • People with the blood type A+ represent about 35.7% of the adult population.
  • People with the blood type A- represent about 6.3% of the adult population.
  • People with the blood type B+ represent about 8.5% of the adult population.
  • People with the blood type B- represent about 1.5% of the adult population.
  • People with the blood type AB+ represent about 3.4% of the adult population.
  • People with the blood type AB- represent about 0.6% of the adult population.

In Japan, there’s a blood type personality theory known as ketsueki-gata. The theory claims that blood types are an important indicator of a person’s personality. It was introduced in the 1920s by psychologist Tokeji Furukawa.

Ketsueki-gata suggests each blood type has specific personality traits:

  • Type A: well-organized
  • Type B: selfish
  • Type O: optimistic
  • Type AB: eccentric

Based on these traits, the theory suggests these blood type matches are most likely to result in happy marriage:

  • O Male × A Female
  • A Male × A Female
  • O Male × B Female
  • O Male × O Female

Ketsueki-gata only accounts for relationships between males and females. It doesn’t account for gender identities that fall outside of the male-female binary, such as genderqueer, bigender, and other nonbinary identities.

Additionally, according to a 2015 study, there’s no scientific consensus of any relationship between personality traits or marriage compatibility and blood groups.

Blood group compatibility for marriage is limited to possible Rh factor incompatibility during pregnancy. And that is further limited to pregnancy where both partners are the biological parents.

Potential problems for Rh incompatibility are easily identified and monitored, and there are treatments for positive outcomes. Rh factor compatibility shouldn’t affect your ability to have a happy, healthy marriage, or to have healthy children with your spouse.

There are some people, such as followers of the Japanese ketsueki-gata, that associate blood types with specific personality traits. But those associations are not supported by recognized clinical research.

There are also couples who value blood group compatibility for the potential of providing blood transfusions to their partner.