A week after the birth of my second child I was back on the trampoline with my daughter - and yes, I had that problem, too. I always made sure my bladder was empty before jumping and worked on the pelvic floor exercises extra hard. I even went so far that I inserted a tampon for the time being on the trampoline because you really have to contract the muscles to keep it in there right after childbirth.
After about three weeks the problem was fixed, it took a daily dose of kegel exercises but it was worth it.
Sit and Stands are good for the pelvic floor, too if you use a heavy barbell and contract the muscles while doing them.
