Childbirth and age are important factors in the occurrence of primary dysmenorrhea

Dysmenorrhea can be divided into secondary dysmenorrhea and primary dysmenorrhea. Primary dysmenorrhea often occurs in young women, starting 6 to 12 months after menarche, and the incidence begins to decline after the age of 30. The pain often begins just before or after the onset of menstruation and lasts for the first 48 to 72 hours of the menstrual period. The pain is often spasmodic and sometimes so severe that the patient needs to stay in bed for hours or days. The pain is concentrated in the middle of the lower abdomen, sometimes accompanied by back pain or radiating to the inner thigh.

Age is an important factor in the occurrence of dysmenorrhea

Women generally experience very little dysmenorrhea in the first few months of menarche, but the incidence increases rapidly afterwards. More women experience dysmenorrhea when they are 16 to 18 years old, and the incidence gradually decreases after 30 to 35 years old. About 40% of women will experience dysmenorrhea in the middle of their reproductive age, and it becomes even lower thereafter. The start of sexual life can reduce the incidence of dysmenorrhea.

Childbirth is another important factor

The incidence and severity of dysmenorrhea in women with a history of full-term pregnancy and childbirth are significantly lower than those without a history of pregnancy or those who have a pregnancy but have a miscarriage or artificial abortion. This is because the adrenergic nerves that control smooth muscle cells in the uterus almost disappear when the term is approaching, and the level of norepinephrine in the uterus also decreases; these nerve endings only partially regenerate after delivery, and the level of norepinephrine in the uterus cannot return to the pre-pregnancy level. This change in uterine neuromuscular activity after full-term pregnancy can explain why dysmenorrhea is reduced or disappears after full-term delivery, but those who have abortion do not have the above changes.