355- A woman with classical CAH is planning pregnancy. What is the probability of
having a child with non - classical CAH?
If a woman has classical CAH, the likelihood of having a child with non-
classical CAH depends on the probability of the woman’s partner being a car-
rier for a gene for non-classical CAH. The frequency of carrier for non-classical
CAH is 1 in 16 in general population as disease frequency is 1:1,000. Therefore,
the probability of having a child with non-classical CAH when a woman has
classical CAH and her partner is carrier for gene for non-classical CAH is 50 %
(one in two) as depicted in the fi gure given below. Therefore, the probability of
having a child with non-classical CAH in the index patient is 1 in 32 (Fig. 10.11 ).Affected Carriers- Normal
- Disease
Fig. 10.11 Inheritance
pattern of CAH in a
couple where mother has
classical CAH and father
is carrier for NCCAH
Affected Carriers- Normal
- Disease
Fig. 10.10 Inheritance
pattern of CAH in a couple
where mother has classical
CAH and father is a carrier
10 Congenital Adrenal Hyperplasia