for me, with quite severe SPD in last preg (on crutches, not able to walk more than 5 mins, off work from about 29 weeks), labour was really difficult, and SPD very painful BUT this may have been because my baby, who had been in perfect position to come out up to waters breaking, suddenly apparently went transverse! according to my labour notes, which midwife and I were revisiting the other day. No wonder that hurt. I was in a lot of pain, and my legs were agony in all the places that the SPD had been affecting. I also had failure to progress, and lots of pushing and no baby coming out, and so ended up with EMCS.
However, if DC had not started shifting around inside me, maybe it would have been OK? Also, my mum, who didn't get SPD in pregnancy, had two very similar long nasty labours ending in EMCS, so I don't think I can necessarily blame the SPD - it just didn't help! Because the pain got so bad, and because there was meconium in waters and baby in distress, I wasn't able to try some of the things I'd been thinking about like moving around, being on all fours, getting in a birthing pool, and I ended up on my back with an epidural. Hopefully you will be able to stay mobile if that's what you'd like.
Good news was that birth went fine, baby and I were both very well as soon as he was out, and amazingly, SPD went completely as soon EMCS over. Pain of recovering from CS was very easy compared to pain of SPD, so I was lucky. I was also really on a high after DC was born, and that helped - I'd been in agony for weeks beforehand, so it was wonderful to have my beautiful baby and be better. I'm pregnant again, and unfortunately I'm getting SPD again, but I didn't suffer after the birth.
Wishing you an easy labour, happy birth and a very swift recovery.