That being said, if you're taking in sufficient calories and eating a good variety of fruits and vegetables, there are no nutrients you would not receive on this diet, and no known reasons to think following a raw diet during pregnancy would lead to any complications.
Anecdotally, there have been an number of women who have given birth to very healthy children after eating only raw foods during their pregnancy.
My generic advice for pregnant women who want to eat raw would be:
1) It's critical that you take in enough calories to fuel not only yourself, but your growing baby. Follow the standard guidelines for increasing caloric intake as your pregnancy progresses.
Many new raw foodists fail to take in enough calories to even fuel themselves properly. Doing this during pregnancy could potentially affect the growth of your baby.
2) Fruits are certainly necessary to meet our caloric needs, but make sure that you're getting 3-6 percent of your caloric intake (1-2 heads, or the equivalent, for most people) of leafy greens and other vegetables per day to make sure you're getting the minerals you need.
3) Ideally a women should be already following a healthy raw food diet before she becomes pregnant so that all the "road bumps," and possible missteps are out of the way before getting into the further complications of being pregnant.