Bridesmaid dress problem

Hey ladies so my MIL is getting married on July. She wants me to be a bridesmaid. Today she called me to have me go try on the dress and all that when I can , but the thing is I’m 24 weeks pregnant due in May. So how will they have it fit to my right size if I have a tummy now 😭 I’m naturally really thin so I just hope it doesn’t end up being loose.