What is a Normal Menstrual Period?
The average American woman will have approximately 450 menstrual periods in
her lifetime. While few women really look forward to this monthly event,
most will have concerns if their periods are earlier, later, heavier, or lighter
than usual. Most women generally become accustomed to what is "normal" for
them, but are not fully aware of the menstrual variations that fall within
the complete range of normal.
First, let's discuss the vocabulary. The term menstrual cycle refers to the recurring, monthly physiologic changes
in a female's body that are controlled by her reproductive hormones. The
term "menstrual period" (aka "menses", "menstruation", or "period")
refers to the 2-5 days of vaginal bleeding at the beginning of each menstrual
cycle. This bleeding is a result of shedding the endometrial lining in a
woman who is not pregnant; pregnant women do not have periods, although they
may experience a normal bloody discharge for a few days near the 6th
week of pregnancy called "implantation bleeding". Normal menstrual cycles
typically occur in non-pregnant females on a monthly basis between puberty
or menarche (when they begin) and menopause (when they end).
While the textbook menstrual cycle is 28 days, the range of normal menstrual
cycles is from 22--35 days. Periods that come every 21 days or fewer are
called polymenorrhea; cycles that repeat more than every 35 days are
called oligomenorrhea. The term amenorrhea refers to periods
that come more than 180 days apart or that are absent. The average age of
menarche in the United States is 12.5, but may occur anytime between ages
8 to 16. The average age of menopause is 51, but usually occurs between ages
45 and 55. The average age of premature menopause or premature ovarian failure
(menopause before the age of 40 for any reason) is 27.
While many women experience may
have heavier or lighter periods, the average blood loss during a normal menstrual
period is about 50 milliliters, with a range of 20 to 80 ml. This is equivalent
to 10 teaspoons or 1.7 ounces of blood lost. While this seems like a small
amount, iron deficiency anemia (IDA) is one of the most common consequences
Created: 6/7/2005  - Donnica Moore, M.D.