After a teen has been menstruating for a few years, her menstrual cycle typically becomes more regular. For most women, a normal menstrual cycle ranges from 21 to 35 days. However, up to 14% of women have irregular menstrual cycles or excessively heavy menstrual bleeding. Most abnormal uterine bleeding can be divided into anovulatory and ovulatory patterns.

• Anovulatory: Irregular/infrequent periods with absent, minimal, or excessive bleeding.
• Ovulatory: Periods that occur at regular intervals but are characterized by excessive bleeding or a duration of greater than 7 days.

The most common menstrual irregularities include:

Anovulatory Bleeding

• Absent menstrual periods: When a woman does not get her period by age 16, or when she stops getting her period for at least 3 months and is not pregnant.
• Infrequent menstrual periods: Periods that occur more than 35 days apart.

Ovulatory Bleeding

• Heavy menstrual periods: Also called excessive bleeding. Although anovulatory bleeding and menorrhagia are sometimes grouped together, they do not have the same cause and require different diagnostic testing.
• Prolonged menstrual bleeding: Bleeding that exceeds 8 days in duration on a regular basis.

Dysmenorrhea: Painful periods that may include severe menstrual cramps.

Additional menstrual irregularities include:

• Polymenorrhea: Frequent menstrual periods occurring less than 21 days apart.
• Irregular menstrual periods with a cycle-to-cycle variation of more than 20 days.
• Shortened menstrual bleeding of less than 2 days in duration.
• Intermenstrual bleeding: Episodes of bleeding that occur between periods, also known as spotting.