There are several things that have to happen to get pregnant. One, a woman needs to ovulate; two, a man needs to have viable sperm; and three, the two have to get together. If you have very irregular periods, it’s hard to know when you are ovulating or even if you are ovulating (source). Having irregular cycles may make it more difficult for a woman to become pregnant than it is for a woman with regular cycles. Dr. Don Aptekar, MD FACOG, explains, “a woman that has regular periods may ovulate 12 times in a year, while a woman with irregular periods may ovulate 6 times a year. Since she has fewer chances per year, it may take her longer to get pregnant.”
Several factors may cause irregular periods, including having an underlying health condition that should be treated. Therefore, you should talk to your healthcare provider to discuss your individual case. To help your doctor make the best assessment, you should track your period for 4-6 cycles and be ready to tell her what your shortest and longest periods are. Your doctor will also want to know if your period is generally heavy or light. This information will help your doctor determine whether or not you are ovulating.
A regular period (the time between the first day of one menstrual flow to the first day of your next menstrual flow) is generally 28 days, plus or minus 7 days. If you find that your cycles are often shorter than every 21 days or longer than 35 days, you may be experiencing irregular cycles (source). It is perfectly natural to start having irregular periods once a woman enters perimenopuase. Perimenopause typically starts when a woman is in her 40s, but it can start in her 30s as well (source).
It is also natural to occasionally have irregular periods. Your periods may be irregular occasionally due to stress, travel or even by different kinds of foods (source). Having chronically irregular cycles and/or very intense and painful periods, however, may not only cause infertility, but may indicate a more serious health problem. Irregular periods may be caused by, for example, thyroid conditions, polycystic ovary syndrome (PCOS) or endometriosis. Irregular periods can also be caused by lifestyle factors such as poor diet, weight (either too high or too low), or intense exercise. For a comprehensive list of conditions that can cause irregular cycles please see here (source).
One of the most common causes of female infertility is PCOS. PCOS can cause women to not ovulate or to ovulate irregularly (source).
If you are not ovulating, you may want to talk to your doctor about either making lifestyle changes and/or taking fertility drugs in order to conceive. If you are ovulating, you probably don’t need to take fertility drugs. Fertility drugs will often shorten the process, but there are risks, including the chance of having multiple births. Fertility drugs encourage the body to make more eggs. So if you don’t want twins or triplets, then Dr. Aptekar advises his patients to wait to find out if they are ovulating first. If you can pinpoint your fertile window (which occurs up to 5 days before ovulation), then you will greatly increase your chances of getting pregnant naturally.
Pinpointing ovulation when you have irregular periods can be difficult, since by definition, they are not predictable. If you and/or your doctor calculate your fertile window based on the length of your menstrual cycles, it represents a statistical prediction and is not based on when you actually ovulate. You may improve your ability to predict ovulation by using your own biological clues. To track your fertility with irregular periods, the American Pregnancy Association (APA), recommends using a combination of your own biological clues: 1) measuring your luteinizing hormone, 2) tracking your cervical mucus, and 3) charting your basal body temperature (source).