Genotype compatibility is about the chance that a couple’s children could have sickle cell disease. If both partners carry a sickle gene (for example AS and AS), each pregnancy has a 1 in 4 (25%) chance of a child with sickle cell disease (SS). If at least one partner is AA, no child will have sickle cell disease, although some may be carriers. Knowing your genotype from a reliable test before marriage helps couples make informed decisions.
What genotype means
Haemoglobin genotype describes the haemoglobin genes you inherited, one from each parent. A is the usual gene. S is the sickle gene. C is another variant. Common results include AA (no variant), AS (sickle cell trait, a carrier), AC (carrier of C), SS (sickle cell anaemia) and SC (a form of sickle cell disease).
Genotype compatibility chart
| Couple | Chance in each pregnancy | Sickle cell disease risk? |
|---|---|---|
| AA + AA | 100% AA | No |
| AA + AS | 50% AA, 50% AS | No (some carriers) |
| AA + AC | 50% AA, 50% AC | No (some carriers) |
| AA + SS | 100% AS | No (all children carriers) |
| AS + AS | 25% AA, 50% AS, 25% SS | Yes: 1 in 4 |
| AS + AC | 25% AA, 25% AS, 25% AC, 25% SC | Yes: 1 in 4 (SC) |
| AS + SS | 50% AS, 50% SS | Yes: 1 in 2 |
| AC + AC | 25% AA, 50% AC, 25% CC | CC is usually mild; not sickle cell disease |
| SS + SS | 100% SS | Yes: all children |
“Chance” applies to each pregnancy separately. A couple who are both AS could have several children with SS, or none.
Why a reliable test matters
- Use an accredited laboratory. Haemoglobin electrophoresis or HPLC is more reliable than older quick tests.
- Recent blood transfusion can give a misleading result; wait about three months or tell the lab.
- If results are unexpected, repeat the test at a different laboratory.
- Get your result in writing and keep a copy.
Options for couples who are both carriers
- Genetic counselling to understand risks clearly
- Prenatal diagnosis during pregnancy (chorionic villus sampling or amniocentesis) at specialist centres
- IVF with preimplantation genetic testing, available at some fertility centres, though costly
- Newborn screening so that a baby with sickle cell disease starts care early
The decision to marry belongs to the couple. Health workers should give accurate information without pressure or stigma.
Living with sickle cell disease today
With early diagnosis, penicillin prophylaxis, vaccines, hydroxyurea, good hydration and access to care, many people with sickle cell disease live into adulthood, work and have families. Stigma and fear should not replace facts.
Frequently asked questions
Can AS marry AS?
They can, but each pregnancy has a 25% chance of a child with sickle cell disease. Counselling helps couples weigh their options.
Can AA marry SS?
Yes. All children will be AS carriers, but none will have sickle cell disease.
Can genotype change?
No. Your genotype doesn’t change. Different results usually mean a testing error or a recent transfusion.
Related reading: Premarital health checks · Sickle cell crisis nursing care · Questions to ask before marriage
Updated 5 November 2026. This guide does not replace genetic counselling.
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