SPD is a painful condition which can occur when the pelvic ligaments soften during pregnancy. Pregnancy hormones cause these ligaments to relax, which allows movement of the pelvic bones during birth. Some women's ligaments soften more than others, and a great degree of softening can cause instability of the pelvic joints, and particularly the pubic symphysis, which is a joint at the front of the pelvis. While it can make pregnancy painful, it can certainly make labour easier as the pelvic ligaments stretch easily to allow the baby's head to pass through. It does not necessarily make labour more painful, although it can do. It is often recommended that women with this condition avoid having an epidural, because if anaesthetised below the waist, they may open their legs too wide, which can make the condition worse. For more info, see discussions on SPD from the UK Midwifery Archives. I suffer from this condition myself and, while I curse it in pregnancy, I love the 2-5 minute second stages it gives me in labour!