Periods are painful primarily because of the chemical prostaglandins, which cause your uterus to contract in order to shed its lining. These contractions can be strong and cause cramping and discomfort. Higher levels of prostaglandins typically mean more intense pain during menstruation. The pain is the result of the uterus tightening and relaxing to expel its lining, and this cramping usually peaks just before and during the first days of the period.

There are two types of period pain:

• Primary dysmenorrhea: Pain caused by normal uterine contractions due to prostaglandins, usually without underlying medical conditions. This type is more common in younger people and may lessen with age or after childbirth.

• Secondary dysmenorrhea: Pain caused by reproductive system conditions such as endometriosis, uterine fibroids, adenomyosis, pelvic inflammatory disease, or cervical stenosis. This pain can be more severe and persistent.

Other factors that can make periods more painful include hormonal changes, structural abnormalities in reproductive organs, and infections. Secondary causes of pain often require medical treatment.

In summary, painful periods are mainly caused by uterine contractions triggered by prostaglandins, which help shed the uterine lining but can cause intense cramps and discomfort during menstruation.