Does your period come every 21 days? Every 30? Don't worry. It's normal, says Lissa Rankin, MD, an OB/GYN physician and author of the forthcoming book, What's Up Down There? Questions You'd Only Ask Your Gynecologist If She Was Your Best Friend. Rankin, whose book will be published by St. Martin's Press in October 2010, is the founder of OwningPink.com and the medical director of The Owning Pink Center, an integrative medicine practice in Mill Valley, California.
"On average, women get their periods every 28 days, but all women are different. Technically speaking, a normal cycle lasts anywhere from 21 to 35 days," says Rankin. When should you worry about irregular periods? Rankin says that if your period timing swings wildly (such as 22 days one month and 35 the next), then you should talk to your doctor to make sure nothing is wrong.
If you are new to having a period, however, variations in your cycle are normal. "It may take a few years for the hypothalamus, pituitary gland and ovaries to mature fully and result in normal, regular monthly cycles," says Rankin.
Your diet and exercise practices can affect your oeriod (and your chances of getting pregnant). "If you're training for a marathon or not eating enough, your body will assume you're not fit to carry a pregnancy. Your estrogen levels may drop, and you may stop ovulating," says Rankin.
What does that mean, exactly? Well, if you work out a lot -- as an athlete might -- you could go years without a period. "This type of menstrual irregularity, called hypothalamic amenorrhea, most commonly results in infrequent or absent periods," says Rankin.
Much like diet and exercise, being too thin can make you skip periods since your body doesn't think you are healthy enough for childbearing.
But being overweight can be a problem, too. "If you're overweight, excessive estrogen can build up in the body, causing periods to be heavy and sometimes irregular (something we call 'menorrhagia' (heavy menses) or 'menometrorrhagia' (heavy, irregular menses)," says Rankin.
Whoa, birth control. It's hard to lump the impacts of birth control into one neat package. Why? Because different forms of birth control do different things to hormone levels. But whatever form you use, you should know that it will have some effect on your cycles.
"Many birth control methods manipulate the menstrual cycle. For example, a woman on the cyclic birth control pill, patch or ring usually has a very predictable 28-day cycle because the hormones are forcing the body into an artificial cycle," says Rankin.
Other forms of birth control, such as getting an IUD can make periods heavier or lighter depending on the type of IUD. Meanwhile, some pills offer a continuous dose of hormones intended to leave you with just a few periods a year.
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