Unfortunately, one answer cannot be given to all women whose menstrual cycles are irregular. Sometimes, irregular cycles are caused by reproductive conditions that can actually affect a woman's ability to get pregnant, like Polycystic Ovary Syndrome. There may be a luteal phase defect where a woman ovulates, but the time from ovulation to menstruation is too short to allow any fertilized egg to implant into the uterus before a period comes along. The key to getting pregnant naturally when you have irregular periods is to know the reason behind your irregular periods.
You can find out if and when you are ovulating through charting to conceive, listening to your body's natural signals that you may be ovulating, and using ovulation tests. With irregular periods, an ovulation calendar unfortunately will not do much for you. You can also get tested for any nutritional deficiencies, and start taking multivitamin supplements and folic acid. Sometimes, problems with eating habits are the culprit. Too much exercise (really fit athletes) or being obese are also possible reasons of irregular periods. Taking a critical look at your lifestyle and assessing how changes could affect your menstrual cycle are always a good idea.
The final tip we have for you may be the most obvious one couples who have regular sexual intercourse, throughout the month, are much more likely to get pregnant, especially if you have a varying cycle and don't know when you may be ovulating.