Both carriers of sickle cell anemia. What can you tell them about their chances of any child of theirs exhibiting this disease?

In theory 25% Please remember these statistics apply to large population and therefore it is possible for a couple with sickle cell trait have children with and without sickle cell disease.
Simple math. Any conception of two sickle cell carriers could produce :sickle cell disease (1/4), carrier(2/4) normal(1/4). It is important to stress, any pregnancy could produce ss sickle cell disease no mater if the previous pregnancy did or did not. Many state newborn screening programs look for ss or s trait. If baby gets a s gene from each parent they will get sick. Carriers generally do not.