It is a condition where intermenstrual cycle is prolonged to more than normal 28 days. But some women have a perfectly normal menstrual cycle at 35 days, without any problem because their fertility is intact and that is why it can not be considered as pathological.
Infrequent menstruation should be diagnosed only if the menstrual cycle is erratic and unduly prolonged and some times it prolonged to three months to four months or longer. This situation is most commonly seen at the time of menarche (first menstruation) or at the time of menopause and which can be regarded as modified amenorrhea. But normal reproductive capacity is possible within this infrequent menstrual cycle and infrequent ovulation.
In the pathological variety of infrequent menstruation the causes and finding on clinical and investigational findings are to some extent similar to amenorrhea and patient is usually obese, poorly developed secondary sexual characters, hirsute, and hypoplasia of genitals. And the most common finding in the investigation of these types of patients is subnormal functioning of ovaries.
In some women the menstruation lasts for only a day or two and the blood loss is also very less and require changing of diapers of only one or two. Scanty menstruation that occurs regularly is not pathological and they are not infertile as the regularity of menstruation proves normal pituitary ovarian cycle. So if a patient of scanty menstruation has normal secondary sex characters it can be considered normal and no treatment is required, other than reassurance. If scanty menstruation is accompanied by irregular menstruation, it is suggestive of primary or secondary ovarian sub function. Depending on the history of menstruation, the primary or secondary ovarian disorder can be determined (if from the beginning the menstruation is irregular and scanty, it is due to primary ovarian disorder and if it starts later it is secondary cause). If the menstruation become suddenly erratic and scanty or no loss, it is suggestive of premature menopause. Then the treatment is same as primary and secondary amenorrhea. The patient and relatives should be convinced on this to the point of their satisfaction.