SL - I am 163cm and was 56kg pre preg. I am still under 70kg at 35.5 weeks. It has nothing to do with your size, more to do with the hormones and the baby's weight on the joint. SPD is when you pelvis is separated more than usual, but still below 9mm separation, which is not as debilitating as DSP (I have a thread about that somewhere) which has put me in a wheelchair for the rest of my pg. The earlier you catch it the less likely it is to get worse. For me it started as feeling like someone had kicked me in the crotch. Generally the best physios to see are womens health or orthopaedic because they do specialise in this sort of thing.

I had SPD with DD2 as well and mine started around the 30 week mark with her. This time it started around 18 weeks and got a lot worse. I had an ultrasound on my pelvic joint to diagnose DSP. My separation at my ultrasound at 29 weeks was 11mm. No matter what anyone tells you pelvic pain like that is not normal, although common, and does need intervention to prevent it getting worse. Provided you can still open your legs when they are symmetrical you wont have problems with a VB.