How to calculate the safe period for women? Women may be at risk of pregnancy during menstruation. Therefore, having sex at specific times outside the menstrual period can effectively avoid unwanted pregnancy. This is the concept of women’s safe periods, which are specific days when it comes to contraception. Since every woman\’s menstrual cycle is different, in order to calculate a woman\’s safe period, we need to know something about the menstrual cycle. 1. Menstrual cycle The menstrual cycle refers to the length of time between two menstrual periods. Normally, a menstrual cycle lasts about 28 days. However, some women\’s cycles can be as short as