The problem started right after Jamie Li delivered her first child. The birth went well, but when she went to use the bathroom for the first time afterward, she noticed she had leaked urine. She didn't worry much. She figured it was probably because of the epidural or the urinary catheter she'd had during delivery. Or maybe it was a side effect of the chemotherapy she'd had after learning she had breast cancer during the pregnancy. Over time, the incontinence improved, though she continued having to wear panty liners every day.

"It's one of those things no one ever talks about, especially young moms," says Li, a 41-year-old cake maker from San Mateo, California. But when she dispensed with that social norm by mentioning what she was experiencing to other women, she discovered she was not alone. Indeed, stress incontinence – the term for when physical stress triggers the passage of urine – affects up to 35 percent of all women at some point. Pregnancy, age, obesity and smoking all can play roles in weakening pelvic muscles and ligaments, leading to the condition.