has part has part towards has modifier menstruation Abnormality of the menstrual cycle Irregular menstruation HP:0000858 Irregular periods UMLS:C0156404 Menstrual irregularity Menstrual irregularities Irregular menses SNOMEDCT_US:80182007 Abnormally high variation in the amount of time between periods. Most women have between 11 and 13 menstrual periods each year. Bleeding usually lasts around 5 days (range: 2 to 7 days). When menstruation first starts, it can take up to 2 years to establish a regular cycle. After puberty, most women's menstruation is regular. The length of time between each period is similar. The normal menstrual cycle length is 28 (+/- 7) days days with the menstruation lasting between 2 and 7 days. It can take up to 2 years from menarche to develop a mature hypothalamic-pituitary-gonadal (HPG) axis. Within 1 year, 75 percent of girls have a cycle between 21 and 45 days. By the fifth gynecological year, 90 percent of girls will have regular cycles. abnormal irregular rhythm