From Tracee Cornforth,
Your Guide to Menstrual Disorders.
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Is your period late? Has it been more than 35 days since your last period? If more than five weeks have passed since the first day of your last period, or if you have reached age 16 and you haven’t had your first period, you should make an appointment to see your doctor for diagnosis. Once menstruation begins, it should occur about every 28 days, except during pregnancy, until monthly periods cease at menopause.

The medical term for the absence of menstruation is amenorrhea. There are two types of amenorrhea –- primary amenorrhea and secondary amenorrhea. Primary amenorrhea occurs if menstruation hasn’t started by age 16. Secondary amenorrhea occurs when periods have occurred but have suddenly stopped.

A third type of amenorrhea called lactational amenorrhea occurs during breastfeeding. Although some women use breastfeeding as a natural contraceptive, it is only effective for the first six months of exclusive breastfeeding. This means no bottles, or supplements –- breastfeeding only. This type of contraception may not be a good idea for many women since ovulation occurs approximately two weeks before menstruation. So you will not realize you have ovulated if you have not had any periods postpartum.

The most common reason women miss their periods is pregnancy. However, there are several other reasons your period might be late. Hormonal disorders such as polycystic ovary syndrome or PCOS can cause amenorrhea, as can hormone-based contraceptives such as oral, injectable, and patch contraceptives, as well as certain types of IUDs.

Other causes of amenorrhea, or late periods, include uterine or cervical infections, and certain chronic diseases and conditions such as lupus, and diabetes. Rarely, tumors of the pituitary gland or problems with the adrenal gland cause amenorrhea.

Do you have a lot of stress or anxiety in your life? If you're under stress or experience anxiety often, you may also experience late periods, or true amenorrhea.

Another area to consider, if you’ve missed your period, is your diet and fitness routine. Girls and women who exercise excessively sometimes don’t menstruate. Amenorrhea is common among women who participate in track and other sports that require intense physical training. Also, if you’ve been trying to lose weight by excessively restricting your calorie intake you can develop amenorrhea. Amenorrhea is common in anorexia nervosa, an eating disorder that causes girls and women who have the disorder to perceive themselves as fat, so they refuse to eat, often until, serious physical consequences occur.

_Sources:

"Menstrual Disorders: Facts to Know"; Healthy Women.org, NWHRC; accessed 09/16/07.

Menstrual Disorders Key Q&A; NWHRC; accessed 09/16/07.

Amenorrhea; MedlinePlus Medical Encyclopedia; accessed 09/16/07.

ACOG Education Pamphlet APO24; Natural Family Planning; accessed 07/24/07.