If the menstrual cycle is regular in 28-30 days, you can calculate the safe period by projection, seven days before and eight days after menstruation belongs to the safe period, that is, from the first day of menstruation, eight days after menstruation including menstruation, at this time there is no ovulation phenomenon, intercourse will not be pregnant. Ovulation is usually about 14 days before the next menstrual period, when the chances of conception are high, such as not planning to have intercourse to take contraceptive measures, or avoid ovulation intercourse, in order to reduce unwanted pregnancy, you can choose ovulation test paper to detect ovulation, or take birth control pills. Unplanned pregnancies are extremely harmful to women’s bodies, especially abortion can damage the uterus, and frequent abortions can easily lead to uterine adhesions, chronic pelvic inflammatory disease, endocrine disorders, and possibly secondary infertility. Although women can calculate the safe period, ovulation can also be affected by some external influences, abnormal ovulation, safe period intercourse contraceptive rate will not reach 100%, for the sake of health best safe period should also take contraceptive measures.