To determine the best time to conceive with irregular periods, it may be helpful to look for other signs of ovulation such as changes in cervical mucus and basal body temperature, says the American Pregnancy Association. Even with irregular periods, keeping a menstruation calendar may help a doctor or specialist to better understand a woman's fertility issues.
A woman with irregular periods generally has a menstrual cycle that is consistently shorter than 23 days or longer than 35 days long, notes Pregnancy Store. This is usually due to a hormone imbalance, which may be caused by a variety of factors ranging from improper eating habits to polycystic ovarian syndrome. Determining the underlying cause of irregular periods may help a woman find out if and when she is fertile and how to improve the chances of conceiving. In order to conceive, sperm cells should be alive in the uterus at the time of ovulation. Therefore, a woman tends to be most fertile a few days before ovulation.
Throughout the menstrual cycle, the consistency and amount of cervical mucus that the body produces changes. During or before ovulation, a woman may notice that the mucus is more plentiful and has a consistency similar to egg whites, explains the American Pregnancy Association. Body temperature may also spike when a woman is ovulating. Measuring body temperature daily or tracking overall temperature for a few months may help a woman notice any existing patterns.