Warning: If you are the sort of person who expects AIBU to be full of deeply important life issues, this is not the thread for you. If you expect deep indignation, this is also not the thread for you. But I blame MN entirely for my situation, so there.
My dear brother has a baby, and it is the most amazing baby in the world, of course. And DB enjoys educating me and DH because we're poor childless fools (and we like the baby).
Now, I know bugger all about having children, I have never been through labour, and I should, I know, confess my ignorance with a becoming modesty.

However: being a fine, upstanding and lazy member of MN, I spend time on here and I watch stuff like Call the Midwife (which I am sure is practically a documentary, naturally) and One Born Every Minute. And sometimes some of it sinks in, sort of vaguely.
So, we were listening to DB monologue chat about his wife's labour, and DH happened to mention a mutual friend who'd had a difficult time because her baby's shoulder got stuck during delivery. So my brother says, 'oh, no, that doesn't happen! You see, the baby can move around during the pregnancy - but when it wants to be born it puts its head down, and straightens out, and it comes out like that, so there is no way it could get stuck. It's all instinct and nature!'
Leaving aside the fact I'm not 100% sure we needed telling most babies are born head first
... AIBU to feel I am quite right that some babies do get stuck during tricky labours and to feel I must bite my tongue and say nothing about this to my brother because he - rightly - will assume I am a childless know-it-all talking bollocks?
He also came out with, 'You see, LRD, you can't really have drugs during pregnancy because if you do, the baby will not learn to breastfeed - if you don't have drugs, the baby knows what to do by instinct.' So, you know, no pressure. 
Now, AIBU to think that if I had never found MN I would never have absorbed any vague inkling that the above information might be in any way incorrect, and I would have trusted by brother and gone around in blissful ignorance?