That it's manageable. When I was transitioning and getting slightly panicky (I was prepared for this through hypnobirthing though so didn't completely freak out!), I said to the midwife 'I'm not sure I can do this!'. She said 'no one has got to this point and not had a baby'. It was the best thing to say to me in that moment as it made me realise that even if my brain is saying no no no, my body was saying yes yes yes!
That I enjoyed birth, I looked forward to doing it again the second time as I knew it would be the last time. I wanted to feel it all!
I still have flashbacks to pooing on the floor when squatting down and pushing baby down. Not my finest moment.
That you don't care you've not shaved your legs or public hair.
That midwives will shoot glances at each other to communicate and unless you tell them to tell you what's happening, they sometimes make the decision to keep info from you that they think will worry you. I had to tell my midwife: just tell me and talk frankly! They can use a lot of annoying euphemisms and flowery language. I asked them not to call me mummy either. That's not my name! They were cool with it.
That arnica tablets do actually help!
That a tens machine helps too.
That one of the hardest bits was the car journey to the labour ward. I had a home birth the second time.
That you can gently remind medical professions you don't want to be on your back. They are very keen on it as it helps them to see but you need gravity on your side!
That hippy dippy hypnobirthing was the best thing I did, despite being a practical, no nonsense, crystal hating pessimist and now I know why people get preachy about it!