I had SPD badly with DS2 and severely to the point on needing crutches and occasionally a wheelchair with the twins. When it came to giving birth there was no extra pain, and in fact birth is often easier with SPD as your pelvis is already open a bit.

The only word of warning is try to avoid an epidural as this will rob you of your pelvic sensation. The pain you currently have is a warning system to go no further, so without that you may open your legs too wide (or have them hoisted into stirrups by a midwife) thereby damaging your pelvis on a much more serious basis.

Giving birth on all fours or in a pool is generally a good way to do it with SPD.

Good luck!

T
xx