5 Things You Didn't Know About Your Period  or for decades --
and you think you're in the know. Then up pops a question from
you or one of your friends that no one can answer with
certainty.  That doesn't surprise gynecologists, who say they
often field menstrual cycle questions from their patients.
Here, three top gynecologists talk about the most common
questions they get about periods and what they tell their
patients.  1. Why do I get PMS?  or premenstrual syndrome,
occurs because your body is sensitive to hormonal changes, says
Richard P. Frieder, MD, a staff gynecologist at Santa Monica
UCLA & Orthopaedic Hospital in Santa Monica, Calif. "In the week
or 10 days before your period comes, hormone levels --
progesterone and estrogen -- are changing rapidly," he says.
That can cause symptoms such as bloating , mood swings, headache
, breast tenderness, and fatigue in some women, he says.  As
many as 90% of women experience some symptoms before their
period, according to a study in the Archives of Internal