Usually when mom who has been coping wonderfully starts to say they can't do it anymore, that's when I seem to notice transition.

Oh, and I think it's absolutely silly to tell a mom having involuntary pushing (especially a multip) to stop. You can't. My first was very much medicalized without necessity, and they told me not to push because they wanted to give me more medicine in the epidural, to which I said, "I'MMMM NOOOOT PUUUUUSHING!!" in a VERY strained voice and they decided to check me and see that he was just about crowning! When a mom tries to resist it, she clenches up which at the very least will make her muscles even more sore the next day!

ETA: I meant to ask if the moms who ended up with swollen cervix had been directed while pushing? Like the whole, hold your breath, chin to chest, count to 10 thing? I like seeing where mom is allowed to push as she feels, without direction. It seems like the body pushes just the way it needs to. Small ones if there's a little 'lip' left to help get it out of the way, etc.