Childbirth is one of the most amazing, life changing experiences a human can experience. It also really, really hurts. Whether or not your child’s birth is medicated, you're bound to experience a degree of pain and discomfort. What you really need is to be surrounded by people that love you and support you, and offer comfort as you undertake labor and delivery. Unfortunately that's not what every mom-to-be experiences. Instead, an unlucky few encounter the cruelest things anyone could do to a laboring woman.
There really ought to be a code of conduct that people must swear they will follow before they're allowed in or around the birthing room or suite of any woman in labor. After all, if you're being trusted to witness someone at their most vulnerable, most stronger moment, you shouldn't underestimate that honor. However, for better or worse the onus is on every pregnant woman to think very carefully about who they want to be with them when they go through childbirth. If someone annoys or upsets you in normal everyday life, I think it's safe to say they're going to drive you crazy in the delivery room.
Personally, I chose my mom to be there while my son was being born, and she was amazing. She kept me hydrated, cheered me on, and calmed my fears. Most importantly, she definitely didn't do any of these truly unforgivable things: