Scientific American is carrying this article summarizing claims that the reason multiple births are on the rise is not related to in vitro techniques, but something else entirely:

Using data obtained from mothers by way of questionnaire, physician Gary Steinman of the Long Island Jewish Medical Center and his colleagues compared the number of twin births from moms who consumed meat and/or milk and those who consumed no animal products at all. They found that the omnivores and vegetarians were five times more likely to have fraternal twins than the vegans.

That's right folks... it's what you eat, not who you are. The scientists think it's related to growth hormones used in agriculture. Personally, I'd like to see more studies to confirm this link before we all start doing Chicken Little impersonations and banning things left and right.

For once.