Ever feel a little bit of pee slip out when you didn't plan on it? No need to blush—it happens to millions of women, and not just the ones in your grandma's bridge circle. A recent study published in the journal Female Pelvic Medicine & Reconstructive Surgery found that 10.3% of women between the ages of 19 and 30 experience urinary incontinence (that's the medical term for unintentional leakage).

Urinary incontinence generally falls into two categories: urge incontinence, which means your bladder fully empties before you're safely over the toilet, and stress incontinence, which usually involves a smaller amount of urine that leaks when pressure is applied to your bladder. Something as simple as sneezing during an allergy fit or jumping during a cardio workout class could cause urine to leak out, says Dr Philip Buffington.

Around 40% of those affected by urinary incontinence experience both of these types, estimates Buffington, though it's difficult to get an accurate picture of just how many women suffer from it. "Women can leak a little bit of urine and put up with it for years, and it doesn't really bother them that much," says Buffington. "It's much more common than you hear reported."

Since the secret's out, here are four reasons why it's happening and what you can do to stop it.

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