I'm 9 months post partum and have never had any urinary incontinence at all during pregnancy or after birth. In fact I had urinary retention after birth and had to be catheterised for two weeks as I couldn't pass urine, this resolved (although I had no sensation for four months). All has been normal since.
This evening I did an exercise class that I've been doing for about 6 weeks, some jumping but not very high impact and I felt some wetness. It didn't feel like I was passing urine, in fact I thought my first post partum period had picked a fine time to show up! But the crotch of my leggings is soaked and it's definitely pee. Luckily it was clubbercise which is done in the dark! 
Lately I've been a bit lax about pelvic floor exercises, admittedly. Is this just what happens if you don't do them, even after 9 months and with no previous leakage? Or should I see the GP in case I have a UTI?