A woman gets pregnant when male sperm and a female released egg unite. Sperm have tails to help them swim to the fallopian tubes and fertilize an egg. The releasing period of the female egg varies among women but on average a woman's egg is released between day 9 to 17 from the day she started having her periods. This differs among women because of varying menstrual cycles. If you have unprotected sex on those days, you are at risk of getting HIV, STDs and pregnancy. You can visit the nearest health facility for more advice on family planning methods to avoid pregnancy.
Attribution: Straight Talk Foundation & Marie Stopes