If you're a teen, missing a period might throw you into a tizzy -- especially if you're sexually active. But while pregnancy is always a possibility if you're having sex, you can miss periods for a number of other reasons. In fact, in the first few years after menstruation starts, irregular cycles and variations in menses flow or length occur commonly. Many teen activities and angst can cause a late or missed period.
Despite the fact that other factors can cause a missed period, if you're sexually active, pregnancy is the most common reason, Summit Medical Group reports. Two out of five teens will get pregnant before age 20, and 80 percent of the time, the pregnancy is unplanned, according to the American Academy of Pediatrics. See a doctor as soon as possible. Home pregnancy tests aren't always reliable; a blood test will give a more accurate reading. Despite what you might have heard, you can get pregnant, even the first time; if you used a douche after; or, even if you used condoms or are on birth control pills.
The teen years have plenty of emotional or physical stress. Worrying about grades, boys, friendships, parents, work and the state of your skin all provide lots of fodder for days full of emotional stress. Physical stresses such as excessive exercise, illness, extreme dieting, binging and purging or weight fluctuations can also affect your hormones and your periods. Stress is actually the second most common cause of late or missed periods in teens, according to the Summit Medical Group.
Low Body Fat
When your body fat percentage drops below a certain level, your body doesn't make enough of the hormones necessary for ovulation. Body fat percentage less than 13 to 17 percent is probably the minimum percentage necessary for normal menstrual cycles, exercise physiologist Dr. William McArdle explains in his textbook, "Essentials of Exercise Physiology." Being an athlete can reduce your body fat percentage; while 2 to 5 percent of women have low body fat, 40 percent of athletes do, according to Dr. McArdle. Eating disorders can also reduce your body fat and your weight to low levels. In these cases, both the physical stress and the low body weight can cause you to stop menstruating.
Polycystic Ovary Syndrome
Some women produce a larger-than-normal amount of male hormones, called androgens. All women produce some androgen, just like all men produce a small amount of estrogen, the main female hormone. High androgen levels in women causes a hormone imbalance that stops you from ovulating and having regular periods. Symptoms of polycystic ovary syndrome, often abbreviated as PCOS, include weight gain, extra hair growth on your face, chest, around your nipples and back, acne, thinning hair and darkened skin around your armpits, neck and breasts called acanthosis nigricans. If you started puberty early, you're higher risk for PCOS. See your doctor if you're missing periods and suspect PCOS.