Situs Inversus Totalis does not have a definite reason or cause for occurring, but there are some suggested beliefs.
One possible cause is that early in the normal development of an embryo, the tube-like structure that becomes the heart, forms a loop toward the left, identifying the left/right axis along which the other organs should be positioned. This cause suggests that at least one gene has to have a role in this process.
Situs inversus does not usually run in families. It is usually an isolated and accidental event occurring in an individual for the first time in the family.
3-5% of people with Situs Inversus have any type of functional heart defect, which is higher than the rate of heart defects in the general population, less than 1%.
It is estimated that about 25% of people with Situs Inversus have an underlying condition called Primary Ciliary Dyskinesia (PCD). PCD is caused by a defect in the cilia that impairs their normal movements.
Situs Inversus Totalis has been estimated to occur once in about 6-8,000 births.
Situs Inversus is currently present in 0.01% of the population in the USA or 1 in 10,000.