The most fertile time of the month is just before or at ovulation. Ovulation usually occurs two weeks before a period starts. Take the number of days in the usual cycle (from the beginning of one period to beginning to the next) and subtract 14. For example, a woman with 32 day cycle would likely ovulate around D18 (32-14=18), while a woman with a 28 day cycle would ovulate around D14 (28-14). Because sperm live longer than the egg does, it is best to have intercourse before ovulation rather than after it, so a woman who ovulates on D14 would have a good chance of conceiving if she has intercourse on either D13 or D14. The ovulation can be predicted by ultrasound, basal body temperature and ovulation prediction kit available in the market.