The 39-year-old's wife collapsed last Wednesday and he will not be expected to return to Manchester until she has made a recovery.
Van der Sar, who is currently out of action with a knee injury as Tomasz Kuszczak deputises, was back in Holland to receive treatment.
Sir Alex said: "Annemarie had a problem over in Holland a week ago and has been admitted to hospital. That is the best place for her to be. They have examined her twice and are trying to get to the root of it.
"I have told Edwin to stay over there. There is no point in him being here. The best thing is for him to be with his wife. Hopefully she will make a good recovery.''