In my pre-pregnancy studies, I have come across many accounts of actual weight loss in pregnancy. Most of these accounts have been from so-called super-sized moms. While not the most flattering term, super-sized mom refers to someone who weighs 300 pounds or more before pregnancy. Some super-sized moms have reported weight loss from as little as 5 pounds to as much as 50 pounds after their baby is born. Larger women getting pregnant need to make sure they find a size-friendly health care provider who understands that their bodies may react differently to pregnancy.
A good resource for plus-sized women interested in pregnacy is: http://www.plus-size-pregnancy.org/