Do I need to do anything different, with regard to diet (not wieghtloss diet) than if I were just pregnant?
In general, just keep following the principles and guidelines of the program and monitor your health, weight etc as you would do with any pregnancy. You should be gaining weight slowly in accordance with healthy guidelines for a healthy pregnancy. I would only be concerned if you stopped gaining the necessary weight and/or lost weight.
The foods recommended here consumed in amounts necessary to maintain a healthy weight, far exceed the RDA/DRI for all nutrients except for VitB12 and Vit D, as we have seen many times here in this forum by those doing the analysis of their diets. Therefore, I do not see the need for a M/V in general, though the decision will be one you have to make.