The probability of pregnancy is very small, around 2-3%, when the condom is worn throughout sex, and the success rate can be around 98% when the condom is not broken. If a condom is not worn throughout sex, there is a possibility of pregnancy. The reason is that during intercourse prostatic fluid will enter the vagina and there will be a small amount of sperm in the prostatic fluid, which also has a certain chance of pregnancy. If there is a delay in menstruation an early pregnancy test is needed. If the condom used is not of good quality, the size of the condom is not suitable, the condom is broken during sex, etc., which can cause the leakage of semen due to the unsuitable type, it can cause pregnancy. The best way to use condoms is to choose the correct method of contraception, and it is recommended to choose the right type and wear condoms during the whole intercourse.