How do you know if your period is regular or irregular? I can't figure mine out!
Laura, 17, Culver City, CA
The fact that the word "cycle" is used to describe a menstrual period makes it seem as though it happens like clockwork every 4 weeks. But the truth is that there is a lot of normal variation in cycle length. A girl's monthly cycle -- the number of days from the start of her period to the start of the next one -- is, on average, 28 days. But cycle lengths vary -- some girls have a 24-day cycle, some have a 34-day cycle. And it's not unusual, especially in the first 2 years after beginning menstruation, to skip periods or to have an irregular menstrual cycle. Other things that affect cycles can be diet, stress, and exercise -- and occasionally illness.
If your period isn't coming regularly, is especially uncomfortable, or has stopped (if you are sexually active this may be a sign of pregnancy), you should see a health professional. Most of the time, though, some variation is normal.