For a woman with regular periods knowing about the ovulatory phase is very simple. For example if you have a 28-day menstrual cycle then ovulation usually happens on the 14th day. If you have monthly periods whether it is a 28 30 or 34-days cycle it is a sign that you are ovulating well. So if you are planning to get pregnant having sex during this time (also called the fertile days) can help you to conceive. However if you have irregular periods it becomes difficult to know about ovulation. But there are ways to know if you are ovulating