When Do Menstrual Cycles Become "Regular"?

My daughter is 14. She has been menstruating for about 7 mos. She is now 3wks late. Is this normal? What factors will cause this besides the obvious? Should I have her seen by a doctor?
Thanks a lot!

Concerned Dad


Robert Steele

Robert W. Steele, MD, is a board certified pediatrician at St. John's Regional Health Center in Springfield, MO. He graduated from medical... Read more

Dear George,

There is quite a bit of variation in how long it takes for a girl to establish the regular menstrual cycle that most women experience in adulthood. And even after the menstrual cycle matures and becomes regular, this "regularity" may differ greatly from woman to woman. This irregularity can give both the parents and adolescent concern because someone feels there is something wrong going on. So, some understanding about the normal variations that occur in early adolescence and young adulthood can help ease some of the anxiety.

The cycles in the early years after menstruation has begun typically are a few days longer than in adults. In addition, the lengths of time for irregularity may commonly be longer in these first couple of years. To understand why this is, first consider the normal menstrual cycle:

Essentially, the menstrual cycle is divided into two parts: 1) the time from the first day of menses until ovulation and 2) the time after ovulation until menses occurs. The variable portion of the cycle occurs prior to ovulation (the first part). The time from when ovulation occurs until the onset of menses (the second part) is relatively constant being about 14 days. Most women have intervals prior to ovulation lasting about 14 days as well. Thus, the complete cycle lasts about 28 days. Obviously, there are many women who follow cycles lasting shorter or longer than 28 days. This variability is primarily due to the time prior to ovulation (the first part). If ovulation occurs earlier than 14 days, then the cycle lasts less than 28 days. If it occurs after 14 days, the cycle lasts longer than 28 days.

During the first two years after a girl begins having periods, up to 50% of the cycles occur without ovulation. By about 5 years after the onset of menses, 80% of the cycles have ovulation occurring within them. Without ovulation, the timing of menstrual cycles is not too predictable which is why periods are so variable during the first two years after they have begun.

George, as you state, there are other reasons why a girl could go for an extended period of time without a period. However, you can see that it is quite normal for a girl to have somewhat irregular periods during the first two years of menses. Barring concern for pregnancy or other health problems that could be a factor in not menstruating, many doctors wait until two periods have been missed before doing any significant evaluation for causes. The most common causes for missed periods in teenagers are pregnancy, stress, and a condition called polycystic ovaries. I suggest you call your daughter's physician to discuss this matter in order that he/she may decide whether or not it is necessary to make an appointment.

Good luck to you.

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