Here's a relatively easy solution for the pregnant bride. We removed the zipper and added loops that can now be laced. We used braid for the loops and 5 yards of 1" double sided satin ribbon for the laces. A modesty panel was made from scraps from the hemming of another gown. This bride decided to have her modesty panel start at her waist leaving the upper lacings to show skin between the ribbon.

This is a before picture for the same type of operation but for a gown that was just too small for the bride.

This is the gown with the zipper removed and the lacings and modesty panel in place. This bride wanted to wear a more supportive bra that hooked across her back so she opted to have her modesty panel cover the whole area behind the lacings.

She also opted to use colored satin for the panel. Here you can see that the color of the modesty panel matches nicely with the amber beads of the gown's lovely beadwork.