It is very common to have irregular menstrual cycles. This means your period seems to come at a different time each cycle with no way to predict when it will arrive (e.g. a 24 day cycle one month, then 41 days the next) or skipping periods entirely. This can be a problem for several reasons. First, it makes it extremely difficult to try to avoid pregnancy if you are not using contraception. Often called the “rhythm method,” this method of pregnancy avoidance involves avoiding sex around the time you may be ovulating. While this method already has a high failure rate, having irregular periods makes it even more likely that you will have an unintended pregnancy. 

To the contrary, another problem with irregular periods is increased difficulty in achieving a planned pregnancy. If you are trying to get pregnant, knowing approximately when you will be ovulating allows you to concentrate your efforts around that time. However, if your periods vary widely, you may have no idea when you will ovulate, making it easier to miss your opportunity to become pregnant.

Having an irregular period can also make it difficult to determine if you are pregnant. Usually, the first sign of pregnancy that women notice is a missed period or being “late.” However, if your menstrual cycle length is never the same, how do you know if you haven’t gotten your period because you are pregnant or because it just hasn’t come yet?

Having an irregular menstrual cycle is quite common in teens and young women and is not a sign of any problem at this age. Usually, a woman’s cycle will regulate with maturity. However, if your period remains (or becomes newly) irregular in adulthood, it could be a sign of a hormonal or other type of problem. Some causes of irregular periods include:

• polycystic ovarian syndrome (PCOS)
• excessive stress
• approaching menopause
• large change in body weight
• pelvic infection
• uterine polyps, fibroids, or cancer
• amenorrhea (see “What problems can occur with menstruation?”)