I'll let AP tell the story:

Palin recently promised in a nationally televised interview that she would release her medical records. Instead, the campaign issued the two-page letter from her physician on the eve of the election.

We have been given no actual records of the last pregnancy, or any reccords at all, although we are told by the elusive Dr. Catherine Baldwin-Johnson that labor was at 35 weeks - not as premature as previously believed (if you research the average weight of full term DS babies, you find, by the way, that Trig was not underweight). There is no time for any reporters to ask any questions, of course, or any time for the questions raised by the pregnancy to be aired in the press. I doubt Baldwin-Johnson will respond to further queries. Obama gave Palin a precedent for this kind of letter as a replacement for records with his equally secretive and brief doctor's note. But at least he did so well ahead of time, and has no serious questions pending about his own health history.

The timing of the release should also surely be interpreted as a giant finger to the press. Releasing this letter one hour before polling day begins and refusing to provide any actual documentation is not an answer. We need documentation to verify the last pregnancy: the amniocentesis results with Sarah Palin's name on them, for example, would be readily available and easy to disseminate, and would help raise awareness of Down Syndrome. So why not give us something? All we have in this literally last minute letter is Baldwin-Johnson's name. We had that already.