If you’re giving birth at home or in a birthing center, you’re typically allowed to wear your own clothes during labor if you want to. But if you’re delivering at a hospital, you should definitely ask your delivery team about their protocol. You very likely won’t be allowed to wear your own clothes if you need to have surgery.
You may want to wear your own nightgown, labor gown, robe, or bra during labor to ensure that you have a comfortable experience, but some doctors don’t recommend it simply because your clothes might get ruined. Delivering a baby can be a bloody process, and you may not want to have that article of clothing covered with blood or other bodily fluids that come out during labor (including, yes, your poop).
You can let your obstetrician or midwife know you’d like to wear your own labor gown, but prepare to hear “no” if it's going to get in the way of your birth.