If a woman already has a child with CAH and becomes pregnant with the same partner, her fetus has a one in four chance of having CAH. For this reason, prenatal testing can be done for some forms of CAH. A health care provider checks for the disorder by using techniques called amniocentesis (pronounced am-nee-oh-sen-TEE-sis) or chorionic (pronounced kawr-ee-ON-ik) villus sampling.1,2,3
- Amniocentesis. This involves inserting a needle into the womb, through the abdomen, to withdraw a small amount of fluid from the sac that surrounds the fetus. The procedure is usually done between the 15th and 20th week of pregnancy.
- Chorionic villus sampling. This is similar to amniocentesis. A health care provider inserts a needle into the womb, either through the abdomen or the cervix, and extracts a small piece of tissue from the chorionic villi (the tissue that will later become the placenta). This procedure is usually done between the 10th and 12th week of pregnancy.
After a health care provider takes a sample using one of these techniques, he or she will perform a genetic test on the sample. This test will reveal whether the fetus has a gene change that causes CAH.
Parents may also choose to wait until birth to have the newborn tested. Talking to their health care providers may help parents identify the option that is right for them.
All U.S. states have neonatal screening for CAH. Infants who test positive need to have follow-up testing done to confirm the diagnosis. If, for some reason, the neonatal screening is negative but there is high suspicion for CAH (such as ambiguous genitalia), further evaluation is also indicated.
Later in Life
Newborns do not show symptoms of nonclassic CAH, and the test done on newborns does not detect nonclassic CAH. Nonclassic CAH is diagnosed in childhood or adulthood, when symptoms appear. To diagnose nonclassic CAH, a health care provider may:
- Ask whether family members have CAH.
- Do a physical exam.
- Take blood and urine to measure hormone levels.
- Do a genetic test to determine if the patient has the gene change that causes CAH.
An X-ray can help to diagnose CAH in children. Because some children with CAH grow too quickly, their bones will be more developed than normal for their age.4