I have been to a fair few births now where I could see the baby was posterior, the labours tend to be very similar, slow and spurious, waters might break but slow to get going, trademark back pain... but the midwives couldn't tell bub was OP or said they they weren't, only later to find out that they were. Even in my own sister's labour, I was fighting so hard to stop them doing one of their 'routine' internals as I knew bub was OP and she wouldn't be as far along as she thought she would be and it would very likely set her back a great deal. Also another midwife suggested pushing when it was not appropriate - OP babies can make women feel pushy too soon. Ive only attended probably one or two labours where babe was OP and mum didn't have pain relief. It can be done, for sure, but it can be more tiring and painful than other labours. So, given the midwife may not even pick it up, your best bet is to educate yourself. Plan an active labour, learn as much from the spinning babies website as you can and do things for OP that will help your labour anyway. Rest when you need to rest, but like the others have said, choose forward positions where you can, give stairs/steps a go during your labour, walk where you can and move that pelvis! Rolls on the ball (or off!) - all these things help a labour anyway.
That also helps! I made it to transition (was in transition for 2 hours) before I needed pain relief, and that was because they were forced to start the synto according to hospital guidelines and I was so bloody exhausted I didn't fight it. So I have some confidence that my pain tolerance is high enough to endure a normal labour and I'd gnaw off my arm to get this bub LOA before onset of labour, then I'd cancel the IOL for sure! Thanks for the help re positions, we will try these things, but it's so hard to keep in mind when the pain keeps building and you want to trust someone else to guide you and kinda let go of that "thinking" and just zone out...