How does the morning after pill affect ovulation?

The MAP works by delaying ovulation -- by temporarily stopping the woman from releasing a egg to be fertilized (and also by stopping the sperm from reaching the egg). It does not cause ovulation. The timing of ovulation will be unpredictable during the cycle you used the morning after pill, and possibly for the following cycle. There is no way of telling with any accuracy when it's going to happen. You may be able to get pregnant right after using it, or you may not release an egg for a few weeks afterwards. Use good contraception, especially during these two months, rather than relying on the calendar to tell you whether or not you can get pregnant. Some women can tell if they are ovulating by their vaginal discharge, but that's not likely to work as well as a sign after the morning after pill.