###Human: How to prevent pregnancy if we have sex the day after period gets over? ###Assistant: Hi. If she has regular periods of 28 days and if she has bled for four days, then it does not come under fertile period. In 28 days cycle, a fertile period comes from day 8 to day 13. She can start taking oral contraceptive pills cyclically, and it gives proper contraception without any stress. On a safer side along with a condom, I-pill (Levonorgestrel) can be used in an appropriate dose within 48 to 72 hours of unprotected penetrative sex without vomiting.