Nothing is known publicly about Ms. Palin’s medical history, aside from the much-discussed circumstances surrounding the birth of her fifth child last April. Ms. Palin has said that her water broke while she was at a conference in Dallas and that she flew to Anchorage, where she gave birth to her son Trig hours after landing.

Last week Maria Comella, a spokeswoman for Ms. Palin, said the governor declined to be interviewed or provide any health records.