So, AU in which Carlisle is present at the birth.

I can just see Edward zooming in to bite through the amniotic sac…

Carlisle: What are you DOING?

Edward: Delivering the baby! There's no time! *opens jaws*

Carlisle: *silently opens drawer and hands Edward vampire-tooth scalpel*

Edward:*stand up sheepishly* ah. Yes, thank you.

Carlisle: If I can come up with the idea of a venom syringe, doesn't it follow that I would consider other surgical instruments? Really, Edward. We are not barbarians.

Edward: *awe/shame* I wouldn't have thought of that.

Carlisle: And this is why I'M the coven leader.