Most women in the middle of their child-bearing years have periods that occur on a fairly regular basis, usually about every 28 days. But life events, including stressful situations, can sometimes disrupt this regularity and cause your periods to occur earlier than expected. Your method of birth control and certain gynecologic or medical conditions may also cause an early period. Contact your doctor if you have early periods on a frequent basis or if your bleeding is excessive or accompanied by significant pain.
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Age and Life Events
Periods are produced by the action of female hormones on the lining of the uterus. When menstruation first starts during the adolescent years, these hormone systems are not yet fully mature and it may take 6 or more years for periods to become regular. Before periods become regular, early periods are common. Periods become irregular again when women enter the perimenopausal years, which typically occurs in their 40’s. Early periods are fairly common at this stage of life as well. Life events can also affect hormone levels and result in periods that occur earlier than expected. High levels of exercise, large changes in weight, any major medical illness, and even mental stress may cause an early period.
Birth control pills can cause a period to arrive earlier than usual, especially if you forget to take 1 or more pills. IUDs are another possible cause of early periods. If you've taken the emergency contraceptive "morning-after" pill known as levonorgestrel (Plan B One Step or Next Choice), you might experience a change in your next period. An article published in the August 2006 issue of "Contraception" found that about 15 percent of women with regular menstrual cycles who took the drug experienced some spotting and either early or late periods in the cycle immediately afterwards.
Certain gynecologic conditions can cause irregular periods or bleeding in between periods that can seem like an early period. In polycystic ovarian syndrome, small fluid-filled sacs called cysts form in the ovaries and abnormal hormone levels are present. You may have polycystic ovarian syndrome if your periods are irregular and you have certain other symptoms, including weight gain or excessive male hormone effects -- such as facial hair or baldness. In endometriosis, cells that normally line the inside of the uterus occur in other parts of the pelvis. If your periods are very painful, you may have endometriosis. Some medical conditions, such as thyroid disease, and certain medications, such as blood thinners, can also cause periods to appear earlier than expected.
Not an Early Period at All
It's also possible that you might misinterpret other causes of bleeding as an early period. For example, if you have become pregnant since your last period, you might have some bleeding before your normal period as the embryo implants into your uterus. This type of bleeding -- called implantation bleeding -- produces less blood than a normal period. Rarely, an infection or cancer might cause a bloody discharge. Although this discharge can appear at any time, it may be noticed at a time when it is misinterpreted as an early period.
What To Do
If your period comes early once in a while, this is likely a normal occurrence and not a cause for concern. But if you frequently have early periods or if you experience other symptoms, such as pain or heavy bleeding, contact your doctor. Keeping a diary or other record of your periods will help determine whether a period is early and may show patterns that help your doctor identify the cause.