i was also anxious about it, i didn't eat heavy that night i wad having the hard contractions mostly fruit and light meal. also during labor i squeezed my buttocks muscles and tried pushing from my vagina, i practiced isolation of the muscles throughout my pregnancy by doing kegels religiously lol

I was told it's unavoidable most of the time, I did and didn't even notice because your pushing the baby out, the nurses are right there to clean up. At that point you won't care yoy just want the baby out :)

Stay hydrated and don't eat anything that would usually upset your stomach or give you soft poop sometimes it's unavoidable just because your body is trying to get a baby out it ends up emptying everything with it