Conventional wisdom states that a woman's menstrual cycle lasts 28 days. A menstrual cycle that lasts 21 to 35 days is considered normal, and the pattern can vary slightly among individual women. Irregular cycles are common and can have multiple causes. Check with your doctor if you have frequent irregular cycles or need further care.
Pregnancy and Breastfeeding
Pregnancy is one of the most common causes of a missed menstrual period. You can expect to miss your period for at least nine months if you are pregnant. Breastfeeding your baby can also cause missed periods. The absence of menstrual cycles during breastfeeding is called lactational amenorrhea.
Birth Control
Hormonal birth control methods can also cause you to miss a menstrual cycle. The types of birth control likely to cause missed periods include the Depo-Provera shot, the IUD and certain types of birth control pills. Birth control methods such as Seasonique allow for only one period every three months.
Stress
Stress can cause missed menstrual cycles. Excessive stress and anxiety could cause you to skip periods. Common causes of stress that could interfere with your menstrual cycle include final exams, financial worries and job deadlines.
Polycystic Ovarian Syndrome
Polycystic ovarian syndrome, or PCOS, is a hormone imbalance. The National Women's Health Information Center says that PCOS affects as many as 10 percent of women. The hormone imbalance causes eggs that would be produced by normal ovulation to form cysts on the ovaries, which disrupts the menstrual cycle. Symptoms of PCOS include irregular periods, acne, excessive hair growth and a tendency to gain weight around the abdomen.
Excessive Exercise
Excessive exercise can cause you to miss your menstrual cycle. Although regular, moderate exercise is important for good health, exercising for several hours each day can disrupt your menstrual cycle. Excessive exercise can also reduce body fat to 15 to 17 percent, which is too low to maintain regular menstruation, according to the National Institutes of Health.
