This condition can only be transmitted through genetic inheritance. It is not contagious and cannot be transmitted through a blood transfusion. People either have the sickle cell trait or they have sickle cell disease. Sickle cell disease is inherited in an autosomal recessive fashion. Put simply, this means that those afflicted with the disease must have inherited two abnormal genes.
Abnormal genes produce abnormal hemoglobin, which in turn produces abnormal red blood cells.
A carrier has one abnormal gene and one normal gene and, therefore, produces some abnormal hemoglobin. However, the amount produced is not adequate enough to result in abnormal functioning cells and these people are asymptomatic. The risk remains the same for each pregnancy regardless of the outcome of the previous pregnancy. Those who have Sickle Cell Disease usually present with the illness at an early age. For those people known to be at risk for acquiring the sickle gene, a simple blood test can be performed to determine a person's status as a carrier.