The success rate of safe period avoidance is still relatively high, about 95%. Under normal circumstances, most women’s menstrual cycle is relatively regular, with a period of about 28-30 days per month. The day of ovulation should be about 14 days before the next menstrual period, and the 5 days before and 4 days after ovulation day belong to the ovulation period. The time outside of the ovulation period, excluding the menstrual period, basically belongs to the safe period, which is generally not ovulation, so the probability of pregnancy is very small even if you have intercourse during the safe period without taking any contraceptive measures, because there are no eggs discharged during the safe period and there is no way for the sperm to combine with the eggs. However, due to environmental factors, work factors, emotional factors and the use of certain drugs, endocrine changes can cause unexpected ovulation. Therefore, the safety period sometimes does not exclude the possibility of accidental ovulation and pregnancy if no measures are taken.