Choosing a maternity bridal dress is not that much different than making the choice when you are not pregnant. The main difficulty you will probably encounter is that your choices will be more limited. You will probably want to stay away from princess style dresses with narrow waistlines. Fit will be crucial, so you should either purchase your dress very close to your actual wedding day or choose a dress design that will allow for the expansion of your figure.
Juliette style gowns with high empire waists and full skirting are ideal for a maternity bridal dress. Not only is this style generally slimming, but if the skirting is full enough, it will help minimize the size of your stomach. In addition, even if the dress is purchased early in your pregnancy, the full skirting will probably allow it to fit even as your girth increases. If you purchase this style of gown early in your pregnancy, but well ahead of your wedding day, it is probably a good idea to buy one that is somewhat loose in the bust, as your bust size will likely increase as your pregnancy progresses. If necessary, you can have it altered just before the wedding.
Another option for a maternity bridal dress is to choose a dress made of stretch fabric. You might want to look at dresses made of spandex, spandex blends, or knit jersey. Just remember that even though a dress of this type may stretch to accommodate your girth, it will likely be form fitting. Every bump and bulge will show, and because of your pregnancy, you will not be able to wear binding undergarments.
Tiered column style gowns are another good silhouette for the pregnant bride. These gowns are usually Grecian style, with tiered layers that drop from the bust down to the floor. The layers usually have slight gathering, and because of the simple lines, this style will sometimes help offset the size of the stomach. You will probably want to choose fabrics that are soft and flowing, such as chiffon, georgette, or voile.
You should probably line up an experienced seamstress well ahead of your wedding day. Even if you purchase a maternity bridal dress that is ready made, there is a very good chance you will need alternations. This will be even more likely if you purchase the dress early. You might even want to consider hiring a seamstress to customize a dress just for you. She will be able to make final adjustments just prior to the day, so not only will you have an original gown, but you will have a better chance of having a dress with a good fit.