Per the NYT, a unique refusal to provide anything at all:
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.
A small correction. Palin did not say she delivered her child in Anchorage. She said she delivered Trig at Mat-Su Medical Regional Center near Wasilla. As for the "much-discussed circumstances" around Trig’s birth, stay tuned.