An Introduction to Ovulation Tracking and Prediction
There are four main ways to track ovulation:
- Temperature method
- Cervical mucus method
- Calendar method
- Ovulation predictor kits (OPKs).
Saliva testing is another method sometimes used. Finally, sometimes ultrasound and/or blood tests are used to help predict ovulation, particularly during infertility treatment, when timing needs to be precise.
These methods can be combined for greater accuracy. For instance, OPKs can help you predict when ovulation might occur ahead of time, while the temperature method can confirm that you actually ovulated.
The Temperature Method
The temperature method is fairly labor-intensive. You must take your temperature every morning, before you get out of bed, using a special basal thermometer. It measures your temperature in smaller increments, compared to regular thermometers. This temperature is known as your basal body temperature (BBT). Your BBT will start out lower at the beginning of your menstrual cycle, but will jump a small but perceptible amount shortly after you ovulate. Many women notice that their BBT falls a few days before their period starts.
The temperature method is inexpensive and can help you identify when in your cycle you are ovulating. However, it is not very useful for predicting ovulation or for achieving or preventing pregnancy. Because your most fertile time is shortly before you ovulate, and since BBT can identify ovulation only after the fact, by the time you can identify ovulation, it's too late. However, over time, BBT charting can help you get to know your cycle well enough to take a good guess at when ovulation will likely occur.
BBT charting can be tricky, and there are various sets of "rules" to help identify whether ovulation has occurred.
The Cervical Mucus Method
The same hormones that fluctuate during the menstrual cycle to produce changes in BBT also produce changes in your cervical mucus. What is cervical mucus, you ask? It is, as the name implies, mucus produced by your cervix, the portion of the uterus that joins the vagina. Why do we produce cervical mucus? Mostly to help sperm travel into the uterus (and also to provide a little lubrication) during your fertile time of the month.
Because cervical mucus tends to change shortly before ovulation, this method gives women the ability to predict ovulation a bit better, compared to the temperature method. However, it can be tricky to learn. You have to be able to identify fertile mucus compared to nonfertile mucus. And yes, there is a certain "ick" factor, particularly for women who are not comfortable with bodily secretions.
Many women who use the cervical method also monitor the firmness and position of the cervix, which tends to change predictably throughout the menstrual cycle as well.
The Calendar Method
The calendar method is another way to track your fertility. With this method, you're basically taking your best guess at when ovulation occurs (and when you are fertile) based on how long your cycles usually last.
If you use this method to try and avoid pregnancy, you'll need to be very careful to keep track of when your period starts for several months, making sure to note exactly how many days each menstrual cycle lasts (the length of time from one period to the next). After you have several months of data, you evaluate it to determine how short your shortest cycle was and how long your longest cycle was. Using these two numbers, you can predict which days are most fertile and which are least fertile. Typically, this method is used to avoid pregnancy, although some women use it to help achieve pregnancy as well.
This method doesn't work well if your cycles are irregular and vary in length, because you will end up with most of your cycle being labeled as "fertile" days, which, of course, isn't truly the case. The more regular your cycle, the better this method will work for you.
The calendar method can be a good, basic place to start when a woman is trying to get pregnant. If using this approach for a few cycles doesn't work, it might be time to try one of the other methods.
The OPK Method (and Other High-Tech Options)
Ovulation predictor kits (OPKs) generally use luteinizing hormone (LH) levels to help predict ovulation. LH peaks shortly before ovulation. With these tests (which generally look and are used much like pregnancy tests), you test your urine at least once a day to watch for this surge in LH levels.
Ideally, you would test every day of your cycle to get a complete picture of what your LH levels are doing, but most OPKs come with a limited number of tests. Unless you have an unlimited budget, though, you'll probably need to shorten the window of time during which you'll use the tests. Follow the manufacturer's instructions for which days to test, which will vary, depending on how many tests come in the kit and the normal length of your cycle. If you test for too few days, however, you're more likely to completely miss your ovulation altogether.
Make sure to read the instructions carefully -- although these tests look like pregnancy tests, they are interpreted differently. While two lines on a pregnancy test means you are pregnant (even if the test line is very faint), seeing two lines on an OPK doesn't necessarily mean you're ovulating. With OPKs, the darkness of the test line helps to determine when your LH is surging.
Keep in mind that ovulation usually occurs within 12 to 36 hours after an LH surge. OPKs are not foolproof. Sometimes, an LH surge occurs without ovulation. Also, different brands may show positive at different LH levels.
If you find that you never get a positive result (in this case, "positive" usually meaning a test line as dark or darker than the control) or if you get a positive result for several days in a row, you might want to switch to a different brand that is more "in tune" with your range of LH levels. In addition, remember that sometimes your LH surge might be brief. If you consistently fail to get a positive OPK but you're sure you're ovulating, consider testing twice a day to try to catch the surge.
If you get confused trying to interpret the lines, consider a digital test. However, some women appreciate being able to analyze (and even obsess) over reading the lines, in which case the traditional OPKs would be preferred. You can also buy fertility monitors, which work by tracking urine LH and estrogen or saliva electrolytes. These are quite expensive, though, so do your research and ask your healthcare provider for advice as well. You can also buy a comparatively inexpensive microscope designed to view your dry saliva, looking for a "ferning" pattern that indicates fertile days.