We hear a lot about the menstrual "cycle," which can make
it sound as though it happens like clockwork. And we say that a
woman who gets her period every 4 weeks is "regular,"
as though there's usually something abnormal about women who don't.
In fact, most women don't get their periods at exactly the same
number of days after the last one.
Let's take a look at what happens when a girl gets her first period
(also known as menarche, pronounced: meh-nar-kee). For most girls,
this happens between the ages of 9 and 16.
Your menstrual cycle occurs in stages, which doctors often talk
about in terms of 28 days. But 28 is just an average figure that
doctors use. Women's cycle lengths vary - some have a 24-day cycle,
some have a 34-day cycle. The only thing you can usually count on
is that if you're not pregnant, nursing, or ill, you will get your
The first day a girl's period comes is Day 1 of her cycle. Around
Day 5, her pituitary gland tells the ovaries to start preparing
one of the eggs they contain for release. One egg will mature completely,
and at the same time the lining of the uterus gets thicker. The
lining becomes thick to prepare a nesting place for the fertilized
egg in the event that the girl becomes pregnant.
On or about Day 14, the egg breaks loose (this is called ovulation)
and makes its way through the fallopian tube into the uterus. If
the egg hasn't been fertilized by sperm, it will disintegrate. About
2 weeks later, the lining and egg leave a girl's body as her period
and the whole thing starts all over again - that's why we use the
All this sounds very neat and orderly, but your body may not follow
this schedule exactly. It's not unusual, especially in the first
2 years after menarche, to skip periods or to have an irregular
menstrual cycle. Illness, rapid weight change, or stress can also
make things more unpredictable because the part of the brain that
regulates periods is influenced by stuff like this.
Some girls always have irregular periods; others get theirs every
28 days like clockwork. Many are regular most of the time, but occasionally
skip a period or get an extra period during times of pressure or
stress. In fact, you may notice that when you go on a trip or have
a major change in your schedule your period is late.
The length of your periods may also vary - sometimes your period
may last 2 days, sometimes 10. That's because the level of hormones
your body manufactures can be different from one cycle to the next
and this affects the amount and length of bleeding.
So how can you tell when you're about to get your period? If you're
not regular, you'll want to pay attention to the clues your body
may give you. These include:
- back cramps or stiffness
- heavier breasts or breast soreness (this will happen after ovulation
and before you get your period)
- acne breakouts
- disturbed sleep patterns
- mood swings
If you're not taking birth control pills, you're not pregnant,
and you're not having other symptoms such as stomach pain, then
it's very likely that your irregular periods are part of the normal
changes that can happen when you're a teen. At some point as you
grow, your cycle will probably settle into a recognizable pattern.
This should happen by 3 years after your first period.
Some teens may develop irregular periods - or stop having periods
altogether - as a result of a hormone imbalance. Disorders of the
thyroid gland can cause menstrual irregularities if the levels of
thyroid hormone in the blood become too low or too high. Some women
have irregular periods because their bodies produce too much androgen,
which is a hormone that causes increased muscle mass, facial hair,
and deepening of the voice in males and the development of pubic
hair and increased height in girls. High amounts of androgen can
also cause hair growth on the face, chin, chest, and abdomen, and
is sometimes associated with excessive weight gain.
If a girl has one of these problems, or if her periods are irregular
for 3 years or more (or for other reasons), the doctor may prescribe
hormone pills or other medications that will help her to have regular
In the meantime, if your periods are irregular, try keeping some
pads or tampons in your backpack, just so you'll have them handy
in case your period comes when you're not expecting it.
It's important to see a doctor if you're sexually active and have
missed a period - this could be a sign that you're pregnant. You
should also see your doctor if you start having periods that last
longer than 7 to 10 days or periods that are accompanied by severe
cramping or abdominal pain.