When does menstruation begin?

On average, menstruation begins around the age of 12. However, in some cases, it might begin as early as 8 years of age. Your first period can last anywhere between 2 to 7 days.

Why are periods so painful?

Periods are sometimes so painful because when your uterus contracts to expel the menstrual discharge, it puts pressure on the surrounding blood vessels. All of which momentarily cuts off the oxygen supply to the uterus muscle causing discomfort.

Why do periods hurt so much on the first day?

The level of prostaglandins in your body is relatively high on day 1 of your periods. This causes your uterus to contract strongly which results in painful periods.