Sickle Cell Disease (SCD) is a genetic condition that affects haemoglobin (responsible for carrying oxygen in the body) in red blood cells. Individuals with SCD have abnormal haemoglobin which distorts the shape off red blood cells, making them crescent moon or sickle shaped. These distorted red blood cells get stuck in the small blood vessels (capillaries) in the body, blocking the blood flow.

Being a genetic disorder, SCD is inherited by a child from his/her parents. Like most genes, haemoglobin genes are inherited in two sets, one from each parent. An individual in whom both the haemoglobin genes are abnormal suffers from Sickle Cell Disease. An individual in whom only one of the two genes is abnormal is said to be having Sickle Cell Trait. While individuals with Sickle Cell Trait do not have symptoms, they can transmit the gene to their child.

If one parent has Sickle Cell Disease and the other is Normal, all of the children will have Sickle Cell Trait. If one parent has Sickle Cell Disease and the other has Sickle Cell Trait, there is a 50% chance of each child having either sickle cell disease or sickle cell trait. When both parents have Sickle Cell Trait, each of their children has a 25% chance of having sickle cell disease.