Dresses with simple skirts and empire waists are the easiest to alter for maternity needs.

Image courtesy DCL

Maternity Alterations

And speaking of labor, maternity alterations are another special-case scenario. The dress has to accommodate a growing bust and belly. "It helps to start by picking the right dress," Krystle says. "It's always best to get a maternity dress for a girl who's pregnant; if she finds out later [that she's pregnant], it's a bit of a guessing game."

A woman doesn't know how her body will change during pregnancy, but a good seamstress can help a bridesmaid fit comfortably into her gown. At Bridals by Lori, the consultants usually advise ordering 2 yards of fabric with the dress. They'll replace the skirt with an empire waist. Of course, this works best for a simple dress without ruching or pleating on the bottom.

On average, Krystle and Courtney estimate that the cost of upgrading a regular bridesmaid dress to a maternity one will run about $80, plus the cost of fabric.