Whether you were asked to be a bridesmaid before you became pregnant, or when you were in the midst of your pregnancy (which is unlikely, since many brides and grooms try to avoid asking a friend to do that), deciding whether to continue on with your bridesmaid responsibilities while you’re growing a new life can be super stressful. On the one hand, you want to be there for your friend during this special time. On the other, you’re probably starting to deal with the anxieties of preparing for a new baby and all of the aches, pains and other woes that can accompany that and make it hard to attend wedding functions and stand for an extended period.
So, if you want my personal opinion, I don’t think it’s a good idea to commit to standing as a bridesmaid when you’re pregnant. A few of the reasons I think it’s a bad idea are that your body will be changing quickly from week to week and that can make dress tailoring difficult, the wedding day is a long, tiring commitment for the bridal party that involves a lot of walking, standing still for extended periods of time and almost always too much heat (why do so many brides plan weddings for 2 PM in the middle of July in a field??)
Thus, I would tell my friend that I’m grateful for the honor, but I need to bow out because of the pregnancy. If you haven’t announced your pregnancy to anyone yet, you still need to let your bride or groom know right away so that they can make other arrangements for their bridal party.
If you feel that you’ll be missing out on the festivities leading up to the big day, and you’re in a financial position to do so - you could always say that you’re not up for standing in the wedding or even committing yourself to going to the wedding (especially if it’s near or shortly after your due date), but that you’d love to help contribute to and attend whatever showers and parties are happening leading up to the wedding. You could even reach out to the maid of honor, let them know the situation and volunteer to say, purchase the put together the bachelorette party favor bags.
This approach will help you to still feel like you’re honoring your friend without over committing yourself when you also have something very big ahead of you!