Ah, well, pregnancy and childbirth increase the risk, Pasta.
Vaginal birth, especially if you need some sort of tool to delivery the baby certainly increases your risk - as does, bigger baby, longer pushing stage, multiple pregnancy, more than one pregnancy.
But, family history, your weight, smoking, heavy lifting and being hypermobile all have an effect too - so, it's perfectly possible that a woman in her 30s without kids, but from a long line of leaky ladies, who's too heavy, smokes like a lum, enjoys deadlifts and is also a gymnast - well, she's gubbed regardless.
Certainly, if you have your baby through the traditional route you are x3 more likely to be incontinent by the time your baby is 21 than if you had a section.
But, equally, if you have few other risks and you #doyerblardyexercises then you could have a whole brood and still be bouncing on a trampoline without a care in the world.
The thing is to actually DO them. Tricky, I know.
@gussiegrips - I tweet, you twitch your twinkle (baboom tssssh)