Having intercourse a week after your period can lead to pregnancy because this is the time when you are in a relative risk period. If you have intercourse at this relative risk, it is possible that the sperm will survive and unite with the egg to achieve a chance of conception. If there is no need to prepare for pregnancy, you can consider taking the oral emergency contraceptive pill to prevent unwanted pregnancy and then perform a termination of pregnancy that will cause essential damage to the uterus, so it is also important to pay attention at this time. In the future, if there is no need to prepare for pregnancy, it is recommended to use condoms for contraception to avoid taking too many oral emergency contraceptive pills, which can interfere with the changes in the menstrual cycle.