Oligomenorrhea literally "not enough menstrual periods" are menstrual periods or menstrual bleeding that is infrequent or that is associated with very light menstrual bleeding. A woman who has oligomenorrhea has less than 10-12 menstrual periods a year, usually between four and nine periods a year and menstrual cycles that last over 35-40 days.  Oligomenorrhea may turn into amenorrhea if there is no period for more than six months.

At the beginning and end of their reproductive lives, around puberty and around menopause it is normal to have irregular menstrual periods. Around puberty different glands like the hypothalamus, pituitary glands, and ovaries take some time to synchronize and produce a regular rhythm. Around menopause the hormones produced by these glands are depleted, the ovaries stop sending eggs. 

There are causes of why a woman may have infrequent menstrual periods and bleeding, why she may have oligomenorrhea and infrequent periods.

The causes of oligomenorrhea include:

• Polycystic ovarian syndrome (PCOS)
• Chronic illnesses, like diabetes, osteoporosis or estrogen-secreting tumors, can also affect menstruation
• Hormone-containing intrauterine devices (IUDs)
• Change in contraceptive methods
• Hormone imbalances like excessive weight changes, stress, eating disorders or severe exercises

Diagnosis And Treatment Of Oligomenorrhea

If you have oligomenorrhea then the first step is to see your doctor who will do a history and physical and probably some tests such as a Pap test, pelvic examination and pregnancy test (just in case), and blood tests to establish the hormonal levels and to rule out various illnesses. The treatment depends on the cause of the oligomenorrhea.