The probability of pregnancy in a single hit depends on the woman’s menstrual cycle and whether she is ovulating or not. A woman with a normal menstrual cycle has a higher chance of getting pregnant if she has sex about 14 days before her period. As long as a follicle is ovulated, there is a chance of pregnancy within 2 days before and after sex. This is because conception is most likely to occur within 48 hours after the sperm enters the woman’s body, and within 24 hours after the egg is released. Women with irregular menstrual cycles have a chance of getting pregnant every time they have sex, and pregnancy is not ruled out as long as there is ovulation. There are individual differences in the probability of pregnancy in a one-time life hit, once the menstrual period is wrong after sex, you need to go to the hospital in time to take a blood test of HCG to confirm whether the pregnancy, avoid self-medication to avoid adverse consequences.