The adrenal glands of babies with CAH are unable to make enough cortisol, which is the principal adrenal gland hormone. In an effort to make enough cortisol, the adrenal gland enlarges, or overgrows. CAH is a genetic disorder. This means that the enzyme defect in CAH is inherited. Inherited disorders are passed from parents to children through genes contained in the egg and sperm which join to form the baby.
Genes come in twos with one gene inherited from the mother and one gene inherited from the father.
Parents of babies with CAH rarely show the condition because each parent has usually only one gene for CAH together with a normal gene. For each baby born of two parents carrying the CAH trait, the odds are one in four. If they want to know whether they carry the trait, there are both gene tests and special hormone tests which may answer this question. It would be very unusual for a person with CAH to marry a person who has CAH or who even carries the trait. The chance of your child with CAH having a child with CAH is roughly one in 200.