Hello, I have gone through your query and understood the concern. In a normal menstrual cycle, the fertile period is the period when ovulation occurs. this happens two weeks prior to the onset of the next period. The week just before the onset of a period is the safe period when an intercourse cannot cause conception. Thus, you had the intercourse during the safe period and so, there is no chance of conception. I would also like to add that the withdrawal bleeding observed after use of the emergency contraceptive pill should not be mistaken for a natural period. This occurs due to the high hormone content in the pill. Please see a specialist if her next period becomes overdue by ten days. Hope this helps.