What are the chances of ovulating eighteen days after first day your last period on a normal 28 cycle?

It is unlikely to ovulate 18 days after the first day of your last period on a normal 28-day cycle. Ovulation usually occurs 14 days before the start of the next period. So, if your cycle is 28 days, you would typically ovulate on day 14. However, it is possible to ovulate earlier or later than day 14, so it is always possible to get pregnant even if you have sex on a day that is not your predicted ovulation day.