Genotype and Marriage: Why You Should Know Your Genotype Before You Marry

Many Nigerian couples are told to “check your genotype” before marriage, and for good reason. Nigeria has the highest number of babies born with sickle cell disease in the world. Knowing your genotype, and your partner’s, helps you understand the chances of having a child with sickle cell disease and make informed choices together.

The best time to find out is early: ideally before a relationship becomes serious, not a few weeks before the wedding.

What is genotype?

In everyday Nigerian use, “genotype” means your haemoglobin genotype: the pair of genes that determines the type of haemoglobin in your red blood cells. You inherit one gene from each parent. The most common types are:

• AA: normal haemoglobin
• AS: sickle cell trait (carrier). People with AS are usually healthy but can pass the S gene to their children
• AC: carrier of haemoglobin C
• SS: sickle cell disease (sickle cell anaemia)
• SC: a form of sickle cell disease

Genotype is different from blood group (A, B, AB, O). Both matter, but for different reasons.

Why genotype matters in marriage

Each child inherits one haemoglobin gene from each parent, by chance, in every pregnancy. The chances are the same for every pregnancy, no matter how many children you already have.

“1 in 4” does not mean one child out of every four children. It means a 25% chance in every pregnancy. An AS + AS couple could have several children with SS, or none.

Which genotypes are compatible for marriage?

If at least one partner is AA, there is no chance of a child with sickle cell disease. When both partners carry an abnormal gene (for example AS and AS, AS and SS, or AS and AC), there is a chance of a child with sickle cell disease.

Whether to marry is a personal decision. Many couples who are both carriers choose to marry and plan their family with medical support. What matters is that you both know your genotypes and understand the risks before you decide.

How to get a genotype test

• The test is a simple blood test, usually called haemoglobin electrophoresis. Some laboratories use a more precise method called HPLC.
• It is offered at most hospitals, diagnostic laboratories and many health centres.
• Use a reputable laboratory. If results are unclear or don’t match an earlier test, repeat it at another accredited lab.
• Both partners should test, ideally together, and keep a copy of the results.

Options for couples who are both carriers

• Genetic counselling: a doctor or counsellor explains your chances and options.
• Testing during pregnancy (prenatal diagnosis): some centres in Nigeria offer tests in early pregnancy to check the baby’s genotype.
• IVF with embryo testing (PGT): embryos are tested before transfer so only those without sickle cell disease are used. This is available at some fertility centres but is expensive.
• Early care for a child with sickle cell disease: with good care, people with sickle cell disease can live long, full lives. Read about sickle cell symptoms, management and prevention.

Know your genotype early

Finding out your genotype only after an engagement can be painful for both families. Testing early, even while single, means you can have honest conversations from the start and make decisions without pressure. Treat your results as health information, not a judgement of anyone’s worth.

Frequently asked questions

Can AS marry AS?
They can, but each pregnancy has a 1 in 4 chance of a child with SS. Speak to a doctor about counselling and your options before planning a family.

Can SS and SS marry each other?
Every child of two SS parents will have sickle cell disease. Couples in this situation should get medical and genetic counselling.

Can AA marry SS?
Yes. All their children will be AS (carriers) but will not have sickle cell disease.

Can my genotype change?
No. Your genotype is inherited and does not change. A bone marrow transplant can cure sickle cell disease in some people, but it does not change the genes they pass to their children. Different results from different labs usually mean a testing error, so repeat the test.

Is genotype the same as blood group?
No. Blood group (A, B, AB, O and Rhesus) is a separate test and matters for blood transfusion and pregnancy.

Planning ahead? Getting married or starting a family? Compare the best HMO plans for families in Nigeria.

This article is for general information and does not replace advice from your doctor or a genetic counsellor.

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