Actually, it depends on the menstrual cycle of a woman. It’s not always definite and therefore, it is very risky. If you are considering having unprotected sex, you are probably thinking of days when the possibility of getting pregnant is less. It might work but this is not a safe method. If you want to avoid pregnancy, then using condom is the safest and easiest method of birth control. https://lovematters.in/en/resource/safe-sex https://lovematters.in/en/resource/fertility https://lovematters.in/en/news/safe-sex-dos-and-donts If you would like to join in on a further discussion on this topic, join our discussion board, "Just Ask” https://lovematters.in/en/forum