Hypomenorrhea orhypomenorrhoea, also known as short or scanty periods, is extremely lightmenstrual blood flow. It is the opposite of heavy periods orhypermenorrhea which is more properly calledmenorrhagia.

In some women it may be normal to have less bleeding during menstrual periods. Less blood flow may be genetic and, if enquiries are made, it may be found that woman’s mother and/or sister also have decreased blood flow during their periods. Pregnancy can normally occur with this type of decreased flow during the period. The incidence of infertility is the same as in women with a normal blood flow. Constitutional scanty menstruation is perhaps best explained by assuming the presence of an unusual arrangement, or relative insensitivity, of the endometrial vascular apparatus.

Reduced menstrual flow is a common side-effect ofhormonal contraception methods, such asoral contraceptive pills,IUDs that release hormones (such asMirena), or hormonal implants such asDepo-Provera. The relatively lowestrogen contained in most hormonal contraceptives reduces the growth of theendometrium, so there is relatively little endometrium left to be shed duringmenstruation. Many women find this side-effect to be a benefit of hormonal contraceptive use.^[1]

Scanty menses or periods can occur normally at the extremes of the reproductive life that is, just after puberty and just beforemenopause. This is becauseovulation is irregular at this time, and the endometrial lining fails to develop normally.But normal problems at other times can also cause scanty blood flow. Anovulation due to a low thyroid hormone level, high prolactin level, high insulin level, high androgen level and problems with other hormone can also cause scanty periods.

Despite these common causes, hypomenorrhea is still technically an abnormality of the menstrual flow, and other underlying medical problems should be ruled out by a doctor.

• One cause of hypomenorrhea isAsherman's syndrome (intrauterine adhesions), of which hypomenorrhea (oramenorrhea) may be the only apparent sign. The degree of menstrual deficiency is closely correlated to the extent of the adhesions.^[2]
• Uterine: Scanty loss sometimes means that the bleeding surface is smaller than normal, and is occasionally seen when the endometrial cavity has been reduced in size duringmyomectomy or other plastic operation on theuterus. However, it rarely indicates uterinehypoplasia because the presence of this condition in a uterus which is responsive to hormones indicates ovarian under-activity, and this manifests itself by infrequent (oligomenorrhea) rather than scanty menstruation.
• Nervous and emotional: Psychogenic factors such as stress or excessive excitement may cause hypomenorrhea. Such factors suppress the activity of the centers in the brain that stimulate theovaries during the ovarian cycle (to secrete hormone like estrogen andprogesterone), and may result in low production of these hormones.
• Lowbody fat: Excessive exercise and crash dieting can cause scanty menstrual periods when the proportion of body fat drops beneath a certain level. It may cause a total absence of periods (also calledamenorrhea).^[3]

Blood tests for the level of hormones such asfollicle-stimulating hormone,luteinizing hormone, estrogen,prolactin,insulin may be conducted. Inpolycystic ovarian syndrome, there will be high levels of insulin and androgens. An ultra sonogram can diagnose the thickness of the endometrium, size of the ovaries growth of follicles, ovulation and other abnormalities. Tests such asdilation and curettage andMRI scans are sometimes needed to determine the cause of scanty blood flow during the periods.^{[medical citation needed]}

Unless a significant causal abnormality is found no treatment other than reassurance is necessary. Otherwise, treatment is determined by the diagnosis of any significant causal abnormality.

• Metrorrhagia

• Medicinenet Article on Vaginal Bleeding