When my wife was pregnant we both did a ton of research because she wanted to keep lifting. It's completely true that being in better shape and being stronger will make both the pregnancy and the birth easier and less prone to complications.
The general consensus is that you can keep doing whatever you were doing before the pregnancy, like lifting and running, as long as it's not something new. There are a lot of changes in the body during pregnancy, and it's not the time to add something new to your routine. Women should NOT take up things like lifting once thye become pregnant, but they can continue if they were already doing it before hand.
This makes things tough for your wife, as you say that she's out shape which probably means that she wasn't doing anything for her health before this point. If that's the case the best thing to do is commit some time to walking. Walking is a great way to keep your body healthy.
As an aside, if she does decide to do a little light lifting, DON'T let her do anything laying flat on her back, as in a bench press. This position cuts off blood to the fetus. Obviously not a good thing. Oddly enough, incline stuff is ok. It's only in a flat position that you can get into trouble.
Another thing to keep in mind is that there are hormones released during pregnancy that will make her body more flexible. This is of course important to the actual birthing process, but also makes pregnant women more prone to injury. This is one of the reasons why she shouldn't start doing new things. If she doesn't have the experience and preexisting strength from lifting before than the increased flexibility can lead to major problems.
Current PRs at 242, raw w/ wraps- 525, 355, 605, 1485
Roboro tui, perimo vester adversarius
(Build yourself, destroy your enemy)