Blood relations

Our body is made up of billions of cells. These cells contain our genes, with information about our hereditary characteristics. We have two copies of each gene: one copy comes from our mother, the other copy from our father. That’s why children often look like their parents: they have half of their genes.

The transmission of genes is random. You can’t influence it. Sometimes abnormalities occur in the genes, also called mutations. Everyone has mutations in their genes. You often will not even notice them, but some mutations cause (serious) disorders. Sometimes a condition only manifests itself if someone has inherited the mutation from both the side of his or her father and his or her mother.

Family members have more similarities in their genes than people, who are not related. As a result, family members are more likely to carry the same mutation in a gene. The closer two people are related, the greater this chance.

If two family members have a child together, both parents are more likely to pass on the same mutation to the child. As a result, cousins, for example, are more likely to have children with a hereditary condition. This is especially true for conditions with an autosomal recessive inheritance pattern.

Globally, the risk of a birth defect affects about 3-6% of all births. This means that 3 to 6 out of 100 babies are born with a condition caused by genetic factors, environmental factors or a combination of both. For children of full cousins, there is an additional chance of about 2 in 100 (2%). The total chance of a hereditary disorder for children of cousins is therefore about 5 to 8 out of 100 (5 to 8%). The closer family members are related by blood, the greater the chance of a hereditary disorder. The less close relatives are related, the smaller the risk.

In some population groups, it is more common for a (cousin) and (cousin) to marry. As a result, they may have a higher risk of certain conditions.

If you would like to find out whether your children are at risk of a hereditary disease, you can examine your own family history and that of your partner together with your general practitioner. This way you can check whether there are any hereditary diseases or disorders in the family. If this is the case, it may be possible to determine how likely future children are to get the disease. This type of research is typically performed by a clinical genetics center.

In some countries, it is common for people to take a genetic carrier test before trying to have a child together. This means that future parents undergo a check to determine whether they are carriers of certain conditions before the pregnancy.