Genotype Compatibility Chart & Checker

Genotype compatibility chart

The table shows every combination of two parents' genotypes and the chance, for each pregnancy, that a child has sickle cell disease.

How the checker works

Everyone has two copies of the gene for the beta part of haemoglobin — one from each parent. "A" is the usual version, "S" is the sickle version and "C" is another variant. A child inherits one copy from each parent at random, which gives four equally likely combinations every time a baby is conceived.

Sickle cell disease happens when a child inherits an S gene plus another S, C or beta-thalassaemia gene. People with one S and one A gene (AS) have sickle cell trait: they are carriers, not ill with the disease (NHLBI).

What to do with your result

• Confirm both results with a test from an accredited lab, and ask whether it also checks for beta-thalassaemia trait.
• Talk to a genetic counsellor or your GP if both of you carry a gene that could combine into sickle cell disease. They can explain options before and during pregnancy, including antenatal screening (NHS).
• Remember the odds reset each pregnancy. Having one child with or without sickle cell disease does not change the chances for the next.