The importance of knowing your baby’s blood type

A mother and father’s genes play a significant role in their baby’s development; from growth in the womb, to blood type. From pregnancy through to their adult life, your child’s blood type is one of the most important pieces of genetic information to be aware of.

Here, we simplify the science behind blood type and explain why more parents-to-be should identify their baby’s type before birth.

How is blood type determined?

Simply put, your blood type is identified from antigens and antibodies found in the blood. However, determining blood type isn’t as black and white as some may think.

Firstly, a person’s type can fall within one of four main blood groups: A, B, AB, and O. These groups identify the different antigens found on red blood cells and antibodies found in plasma. For example, blood group A has A antigens on the red blood cells with anti-B antibodies in the plasma.

As well as falling into the A, B, AB or O group, blood can contain a protein called the RhD antigen. This Rh factor determines whether your blood type is positive (+) or negative (-) [1].

So in total, there are 8 blood types:

A RhD positive (A+)
A RhD negative (A-)
B RhD positive (B+)
B RhD negative (B-)

O RhD positive (O+)
O RhD negative (O-)
AB RhD positive (AB+)
AB RhD negative (AB-)

How is blood type inherited?

The blood groups that make up a person’s blood type are 100% inherited from their parents. Each parent passes on one of two ABO alleles (variant of a gene) to their baby. A and B are dominant, O is recessive. Environmental factors mean that some blood types are more likely to be passed on, which is why 36% of the UK has O+ [2].

To paint a clearer picture, this chart shows your baby’s potential blood type based on those of their parents:

Chart predicting a child's blood type

Maternal blood type during pregnancy

It’s worth knowing that, in rare cases, maternal blood can be incompatible with baby’s blood, leading to complications if blood is mixed during pregnancy. This incompatibility occurs when a Rh Negative woman has a Rh Positive baby, or vice versa.

Rh Positive is when proteins appear on the surface of the blood cells. Rh Negative patients are those who do not carry the protein. When a Rh Negative woman gives birth to a Rh Positive baby, this is called Rh incompatibility….the Rh Negative mom will treat the Rh Positive proteins found in the baby’s blood as foreign, and will make antibodies to attack them.

– Ginny Harrington, Obstetrics and Gynaecology Nurse

Pregnancy complications can also arise from ABO incompatibility between mother and baby. For example, if the mother is O+ but the baby is A+. In this case, the mixing of blood types can cause jaundice in the baby.

To catch potential incompatibility early, all pregnant women will receive a maternal blood test during pregnancy by their doctor.

Why should you know your baby’s blood type?

There are two key reasons to find out your baby’s blood type.

Blood type and medical treatments
The most obvious reason involves potential emergencies. If your child requires emergency medical treatment in the future, knowing their blood type can speed up the search for a suitable blood transfusion. Using the wrong blood type during transfusion can be fatal.

Blood type and future health
Ongoing research suggests that certain blood types may be at higher risk for developing certain health conditions [3].

In 2012, a study found that those with blood type AB have a 23% higher risk of developing cardiovascular disease compared to those with blood type O [4].

Those with AB blood type may have a higher risk of stroke than other blood types according to a 2014 study [5]. This could be due to higher levels of clotting protein in this type.

A 2015 study found that those with type O blood were at a decreased risk of developing type 2 diabetes [6].

The American Cancer Society has identified that those with type A blood have a higher chance of developing stomach cancer, for reasons that are not yet understood [7].

In the case of all studies above and more, it’s important to remember that all research is still in preliminary stages. No matter your genetic predisposition, healthy lifestyle choices are key to prevent future illnesses.

Taking the blood type test

In the UK, your baby’s blood type is not routinely tested on the NHS. However, you can opt for a private test at a small cost. At Future Health Biobank, we can reveal your baby’s blood type as part of our cord blood banking service, using your cord blood sample.

Speak to our Customer Care team on 0115 967 7707 or email to learn more.

[1] [2]
[3] [4]
[5] [6]