Irregular periods (aka irregular menstruation, irregular cycles) is irregular/abnormal variation in length of menstrual cycles, but can also be used to refer to other conditions that mimic it.

Variations in cycle length, between the shortest and longest cycle:

• <8 days, is normal
• 8-20 days, is moderate irregular
• 21+ days is very irregular

Alternatively, a single menstruation period is irregular if it is <21 days, or >35 days. However, if it is regularly <21 days, it is polymenorrhea (aka frequent periods); or if regularly >35 days, is oligomenorrhea.

• Metrorrhagia (vaginal bleeding between expected menstrual periods)
• Oligomenorrhea (infrequent menstruation, >35 days, thus only permitting 4-9 periods in a year)
• Polymenorrhea (intervals <21 days)

• Hx:
  • LMP
  • Last normal LMP

• Metorrhagia
• Oligomenorrhea
• Polygomenorrhea