Menstrual cycles vary in length from one woman to the next.
They may occur at the same time each month or be irregular.
Typically, a cycle occurs about once a month, but can be as
short as 21 days or as long as 35 days and still be
considered normal. Menstrual flow lasts about 3 to 7 days. A
menstrual period is considered late if it is 5 or more days
overdue according to your usual pattern of periods. A period
is considered missed if there is no menstrual flow for 6 or
more weeks.
What is the cause?
A late or missed period could be caused by any of the
following:
Pregnancy
This is the most common cause of missed periods in teenage
girls. If you have had sex even once in the past several
months, see your doctor for a pregnancy test before you
consider any of the other possible causes.
Stress
Stress is the second most common cause of late or missed
periods in teenagers. It may be emotional stress (for
example, breakup with a boyfriend or final exams) or
depression. Or it may be physical stress to the body, such
as a severe illness, a sexually transmitted infection, rapid
weight loss or gain, or strenuous exercise. Dieting or
binging and purging may interrupt menstrual cycles. Changes
in your usual routine (for example, going on vacation) may
also cause your period to be late or missed.
Normal development
During the first couple of years of menstruation many
teenagers have irregular periods. During this time the
body's hormones are not yet "fine-tuned," so the ovaries may
not release an egg once every month. As a result, your
cycles may be irregular, occurring as close together as
2 weeks or as far apart as 3 months.
Hormone imbalance
Hormone imbalance is rarely the cause of missed periods.
In teenagers, polycystic ovary syndrome is the most common
type of hormone imbalance that affects the menstrual cycle.
Polycystic ovaries may cause irregular cycles, increased
body hair, acne, and weight gain.
Sometimes when you stop taking birth control pills you may
have a temporary hormone imbalance and loss of periods. If
you are having sex, be sure to use another reliable method
of birth control because you could still become pregnant.
Problems of the thyroid gland, pituitary gland, adrenal
glands, or ovaries can be rare causes of irregular periods.
How do I know what the cause is?
Pregnancy: A positive pregnancy test is the only way to be
certain of pregnancy. It is best to see your doctor for a
pregnancy test because home test kits can be confusing and
give misleading results. In addition, it's important to
have a supportive person available to answer all your
questions if you are pregnant. Breast swelling, weight
gain, and nausea are additional signs of pregnancy. You may
wish to have a parent (or other adult you trust) go with
you.
Stress: Some stress is a normal part of daily life. Only
you can know if you are under too much stress. Read the
paragraph about stress under "What is the cause?" Consider
whether any of these events have happened lately in your
life.
Normal development: If your doctor finds nothing abnormal
during your physical exam and you've been having periods for
2 years or less, your irregular periods may be part of your
normal development. Remember, if you have had sex, go to
your doctor's office for a pregnancy test when your period
is late for you, even if you normally have irregular cycles.
Also, if you are having sex, read information on birth
control or discuss it with your health care provider.
Hormone imbalance: If you have missed several periods
without an explanation, your doctor can check your ovaries
and look for any signs of hormone imbalance. Blood tests
can be done to measure hormone levels.
When will my period return to normal?
Pregnancy: It is important to identify pregnancy early so
that you can discuss the options available to you and start
prenatal care. Early prenatal care helps ensure a healthy
baby. Call your doctor if you have any bleeding during your
pregnancy. You will not have a normal period until after
the baby is born.
Stress: Your periods should return when the activities or
situations that are stressing you are eliminated or changed.
Normal development: Most girls' menstrual cycles become
fairly regular as their hormone levels become mature and
synchronized. A few women will continue to have irregular
cycles as their normal pattern.
Hormone imbalance: Most often a hormone imbalance can be
treated after your doctor discovers the cause.
How can I take care of myself?
Keep a calendar of when your periods occur and how long
they last. This information can help your doctor make a
correct diagnosis. Take it to your appointment.
Eat healthy foods and keep your weight steady. If you
are overweight, a balanced diet and regular exercise
will help you lose weight slowly (no more than 2 pounds
a week). If you are underweight, eat more.
If you follow a strenuous exercise program, consider
cutting back until your periods come back.
If you have sex, always use birth control. Talk to your
doctor about the available methods.
If you think you might be pregnant, get a pregnancy test
whenever your period is 5 or more days late. Don't
wait. Confidential testing and counseling are available
in most doctors' offices and clinics. Take your first
morning urine specimen with you for the test. Keep it
refrigerated until you take it in.
When should I call my health care provider?
Call during office hours if:
You think you might be pregnant.
You have had sex and your period is at least 5 days late.
Your period does not return within 6 weeks.
You need help with gaining or losing weight.
You need help for binging/purging or excessive dieting.
You need help for stress or depression.
You have an abnormal vaginal discharge or abdominal
pains.
You develop excessive facial or body hair, significant
acne, trouble with your eyesight, persistent headaches, a
deepening of your voice, a coarsening of your skin, hot
or cold sensations when no one else feels them, or other
symptoms that concern you.
Your period does not return within 6 months after
stopping birth control pills and you aren't pregnant.
You have other questions or concerns.
