Normal menstruation parameters

Parameter	Normal	Abnormal
Frequency	≥24 and ≤38 days	Absent (no bleeding): amenorrhea
		Frequent (<24 days)
		Infrequent (>38 days)
Duration	≤8 days	Prolonged (>8 days)
Regularity	Regular: shortest to longest cycle variation: ≤7 to 9 days^*	Irregular: shortest to longest cycle variation: ≥10 days
Flow volume (patient determined)	Patient considers normal	Patient considers light
Flow volume (patient determined)	Patient considers normal	Patient considers heavy
Intermenstrual bleeding (bleeding between cyclically regular onset of menses)	None	Random
	None	Cyclic (predictable): Early cycle Mid cycle Late cycle
Unscheduled bleeding on combined estrogen-progestin contraceptives: oral, vaginal rings, or transdermal patches	For cyclic regimens: monthly withdrawal bleed during placebo pills	Bleeding or spotting during hormone-containing pill days
	Continuous regimens (daily hormone pills, no placebos): eventual amenorrhea	Bleeding or spotting that persists after 3 to 6 months

IUDs: intrauterine contraceptive devices.

* Normal variation depends on age; these data are calculated excluding short and long outliers.

Data from:

Fraser IS, Critchley HO, Munro MG, Broder M. A process designed to lead to international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding. Fertil Steril 2007; 87:466.
Fraser IS, Critchley HO, Munro MG, Broder M. Can we achieve international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding? Hum Reprod 2007; 22:635.
Fraser IS, Munro MG, Broder M, Critchley HO. International recommendations on terminologies and definitions for normal and abnormal uterine bleeding. Semin Reprod Med 2011.

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