Definition

Medical dictionaries define oligomenorrhea as infrequent
or very light menstruation. But physicians typically
apply a narrower definition, restricting the diagnosis
of oligomenorrhea to women whose periods were regularly
established before they developed problems with
infrequent flow. With oligomenorrhea, menstrual periods
occur at intervals of greater than 35 days, with only four
to nine periods in a year.

Description

True oligomenorrhea can not occur until menstrual periods
have been established. In the United States, 97.5% of
women have begun normal menstrual cycles by age 16. The
complete absence of menstruation, whether menstrual periods
never start or whether they stop after having been established,
is called amenorrhea. Oligomenorrhea can become
amenorrhea if menstruation stops for six months or more.

It is quite common for women at the beginning and
end of their reproductive lives to miss or have irregular
periods. This is normal and is usually the result of imperfect
coordination between the hypothalamus, the pituitary
gland, and the ovaries. For no apparent reason, a few
women menstruate (with ovulation occurring) on a regular
schedule as infrequently as once every two months. For
them that schedule is normal and not a cause for concern.
Women with polycystic ovary syndrome (PCOS)
are also likely to suffer from oligomenorrhea. PCOS is a
condition in which the ovaries become filled with small
cysts. Women with PCOS show menstrual irregularities
that range from oligomenorrhea and amenorrhea on the
one hand to very heavy, irregular periods on the other.
The condition affects about 6% of premenopausal
women and is related to excess androgen production.
Other physical and emotional factors also cause a
woman to miss periods. These include: