I mean, I do believe it is possible for brides to make explicit requests of their wedding party that are rude or deeply inappropriate (see: several entire websites for examples.)

And they don't have to all give up drinking with the friends group for the entire pregnancy just because she does; if the bride demanded that, it would be on the edge of unreasonable (although it would certainly be sweet if they did!)

But, yeah, ffs, she's the guest of honor and it's a perfectly reasonable request!