Each menstrual cycle involves the intricate interplay of several hormones and tissues, including the pituitary gland, ovaries and uterus. Considering the complexity of these processes, it's not surprising that they sometimes go awry and lead to an early period and cramps. A variety of factors and circumstances can lead to this situation. An occasional early period is usually nothing to worry about but ongoing menstrual irregularity might signal an underlying health concern.
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The most common reason for an early period in women not using hormonal contraception is simply a short cycle. Some factors that might be associated with short cycles include:
- Age 35 or older
- Drinking more than 1 alcoholic beverage per week
- Prior long menstrual cycle
- Lack of physical activity
There is usually no clear cause for an occassional short cycle. It likely just represents a minor glitch in one of the many processes involved in the timing of your period.
An early period with light bleeding and mild cramping might not be a period but rather pregnancy implantation. Ovulation typically occurs midcycle, around day 14 in a 28-day cycle. If fertilization occurs, the embryo normally implants into the uterine wall approximately 6 to 10 days later, roughly day 20 to 24 in a 28-day cycle. Some women experience minor bleeding and cramping with implantation, which can easily be mistaken for a light, early period.
Contraceptive Side Effects
An early period and cramps could be a side effect of your birth control method if you have an intrauterine device (IUD) or hormone implant, or use the hormone shot. Irregular bleeding and cramps are common in women with an IUD in the first few months after insertion. These side effects occur more frequently with the copper IUD (ParaGard) than hormonal IUDs (Liletta, Kyleena, Mirena, Skyla). The hormone implant (Nexplanon) and hormone shot (Depo-Provera) can also cause irregular bleeding that might be accompanied by cramps. With each of these forms of contraception, irregular bleeding tends to taper off with continued use.
Endometriosis and Fibroids
With endometriosis, uterine lining tissue grows in other locations, usually in the pelvis. Roughly one-third of women with endometriosis experience irregular bleeding, which might manifest as an early period. Menstrual cramps can be intense in women with endometriosis.
Roughly one-half of women with uterine fibroids -- noncancerous tumors of the muscular wall of the uterus -- experience symptoms. These may include irregular bleeding and cramps, which can be severe.
Next Steps and Precautions
If you experience an early period every once in a while, it likely does not signal a serious health concern -- especially if it might be related to your birth control method or you're approaching perimenopause. See your health care provider if your periods are consistently irregular; your bleeding is heavy; your cramps are worsening or severe; or you think you might be pregnant.
Reviewed and revised by: Tina M. St. John, M.D.