Coming from a cousin of a gynecologist. Nowadays it's practically impossible, in a developed country, to fake a pregnancy.
Pregnancies are carefully monitored from the very beginning and if there is a miscarriage or a problem in pregnancy, is carefully recorded. For those who think that she may have bribed the doctors to do that, think twice. Doctors, if caught(and it's VERY EASY that they are), can be taken away their licence for life. In other words, they can't take up medicine again. Honestly, I don't think that Palin is rich enough to bribe so many people and make it profitable. The risk is too high, both for the doctors and the people living around(who have had to see her pregnant),and for her, for that matter. If there was no pregnancy, she could just shut up. The extra brownie points she could gain with that can be taken away as easily because, honestly, in those circumstances, it's easy to demonstrate that the baby doesn't exist and neither her pregnancy and her discredit and her party's is too much. It just doesn't compensate. No matter how much money they have, which wouldn't cover all the people they would have to bribe(and it just doesn't cover only doctors but also those civil servants in charge of the census bureau, staff in her post, neighbours, technicians and staff working in the hospital, etc..........)
Second, when a baby is born, there is an OBLIGATION to the parents to register the baby in the census bureau. So, it would be fairly easy to check out. At local level, still, papers may disappear but not at state level.
Besides, there is no motivation. She was nominated as VP just three days ago and MacCaine as president early this year. Pregnancy takes nine months to come into term and, if she wasn't pregnant, don't you think that people around her, those who don't sympathise with her, wouldn't have already spoken?. You know, how much money and influences can you move for such a trivial, relatively speaking, matter?. Sorry guys, conspiracy theories work that way.
It sticks out a mile that the guy can't get pregnant. To begin with, if wearing loose clothes(and, having been a mother myself, I can talk from experience, many women who have just given birth tend to do that), nobody remarks if you're preggo or not.
Second, three days is the time women spend, on average, in hospitals after giving birth. There is no obligation to take maternity leave inmediately. If she wanted to come back to work immediately, she could with no problem.