In Nigeria, couples are often asked “What is your genotype?” before marriage. This refers to the type of haemoglobin, the oxygen-carrying protein in red blood cells, that a person inherited from their parents. Knowing both partners’ genotypes shows the chance that a child will be born with sickle cell disease, a serious inherited blood disorder. Nigeria has more babies born with sickle cell disease than any other country, so this knowledge matters.
Key facts
- Everyone has two haemoglobin genes, one from each parent.
- People with genotype AS or AC are healthy carriers.
- When both parents are carriers, each pregnancy has a 1 in 4 chance of a child with sickle cell disease.
- A reliable genotype test uses haemoglobin electrophoresis or HPLC at a reputable laboratory.
- Knowing your genotype gives you choices. It does not decide your future for you.
Understanding the letters
- A: normal adult haemoglobin
- S: sickle haemoglobin
- C: haemoglobin C, another variant common in West Africa
So the common genotypes are:
- AA: normal
- AS: sickle cell trait, a healthy carrier
- AC: haemoglobin C trait, a healthy carrier
- SS: sickle cell anaemia
- SC: sickle-haemoglobin C disease, a form of sickle cell disease
- CC: haemoglobin C disease, usually mild
What are the chances for our children?
These chances apply to each pregnancy separately. Having one child with SS does not mean the next child will be AA.
- AA + AA: all children AA.
- AA + AS: 50% AA, 50% AS. No child will have sickle cell disease.
- AA + SS: all children AS (carriers). No child will have sickle cell disease.
- AS + AS: 25% AA, 50% AS, 25% SS.
- AS + AC: 25% AA, 25% AS, 25% AC, 25% SC (sickle cell disease).
- AS + SS: 50% AS, 50% SS.
- SS + SS: all children SS.
Interactive tool
Genotype calculator
Choose each partner's genotype to see the chance of each genotype in every pregnancy.
These chances apply to each pregnancy separately. Confirm genotypes with haemoglobin electrophoresis or HPLC at a reliable laboratory, and speak to a health worker or genetic counsellor about your options. This tool does not replace medical advice.
Getting tested
- Ask for haemoglobin electrophoresis or, where available, HPLC, at a hospital or accredited laboratory.
- Results from quick “solubility” or “sickling” tests alone cannot tell AS from SS, and cannot detect C. They should not be relied on for marriage decisions.
- If results differ between laboratories, or seem unexpected, repeat the test at a trusted hospital laboratory.
- Test early, ideally before a relationship becomes serious, so there is time to understand the results.
- Some people also carry beta-thalassaemia, which can combine with S to cause disease. Your doctor may suggest further tests.
Options for carrier couples
If both partners are carriers, the decision about marriage and children belongs to the couple. Genetic counselling helps you understand the facts and your options, which may include:
- Having children naturally, understanding the 1 in 4 chance in each pregnancy, and planning early specialist care if a child has sickle cell disease
- Prenatal diagnosis by testing the baby during pregnancy, offered at some Nigerian centres
- IVF with preimplantation genetic testing (PGT), where embryos are tested and only unaffected ones transferred. It is available at some fertility centres but is costly. See our infertility guide.
- Using donor sperm or eggs, or adoption
Children with sickle cell disease can live long and fulfilling lives with early diagnosis and good care, including newborn screening, preventive medicines and hydroxyurea.
Common myths
- “Genotype can change.” Your genotype is fixed for life. A different result usually means a testing error, or a recent blood transfusion.
- “AS is a weaker genotype.” People with AS are generally healthy and lead normal lives.
- “Prayers or herbs can change a child’s genotype.” Genotype is inherited and cannot be changed by any remedy.
- “Sickle cell disease is caused by witchcraft.” It is a genetic condition passed from parents to children.
When to see a health worker
Get your genotype tested if you do not know it, especially before marriage or planning a family. If both you and your partner are carriers, ask for referral to genetic counselling and a haematologist or obstetrician experienced in sickle cell disease.
Frequently asked questions
Can two AS partners have all AA children?
It is possible, because each pregnancy is independent, but each child still has a 1 in 4 chance of SS.
Should my blood group also be checked?
Yes. Rhesus (Rh) blood group matters in pregnancy. Rh-negative mothers can receive an injection to protect future babies. This is separate from genotype.
Related guides
Sources
- World Health Organization: Sickle-cell disease fact sheet
- WHO Regional Office for Africa: Sickle cell disease
- NHS: Sickle cell disease
- NHS: Thalassaemia
