Many couples rely on ovulation predictor kits, or OPKs, to identify when the woman is most fertile. OPKs can detect a surge in the production of luteinizing hormone (LH), which occurs roughly 36 hours before ovulation. By timing intercourse shortly after the LH surge, you can increase your odds of bringing sperm and egg together at the time when conception is most likely to occur.
Sounds easy, right? In a perfect world, OPKs would infallibly detect ovulation, and ovulation would inevitably lead to pregnancy. The reality is more complicated, so be sure to consider the pros and cons of OPKs before trusting your fertility exclusively to this method.
1. OPKs are more precise than other methods of monitoring ovulation. Used correctly, the major-brand OPKs are more than 97 percent effective in detecting an LH surge, which is used as a marker for ovulation.
2. OPKs are convenient. OPKs are used only in the middle of your cycle, during the time when you would be most likely to ovulate (note that it helps to have a sense of your typical cycle length, so start keeping track now if you haven't already). Other methods, such as charting your basal body temperature (BBT), require a daily commitment.
3. OPKs are widely available. You can get them over the counter at drugstores, pharmacies, and even major supermarkets and convenience stores, without a prescription.
4. OPKs are easy to use. Ovulation kits are similar to home pregnancy tests -- you simply urinate on the test stick, activating a chemical that can detect your LH surge. Most OPKs contain between five and nine test sticks.
1. OPKs do not test for ovulation. Ovulation predictor kits measure the LH surge that precedes ovulation, but can't confirm whether you have actually ovulated. Occasionally, an egg fails to emerge from its follicle after the LH surge has occurred, a condition known as LUFS (luteinized unruptured follicle syndrome).
2. OPKs don't indicate whether cervical mucus is conducive to fertilization. The mucus produced by the cervix in midcyle, which you experience as vaginal discharge, must have a certain consistency (clear and elastic, like egg whites) in order to provide a fertile environment for sperm to swim through. OPKs do not monitor cervical mucus.
3. OPKs don't work when certain fertility drugs are present in the system. OPKs do not function reliably when injectable fertility drugs such as Pergonal or the hormone hCG (e.g., Profasi) are present in the system.
4. OPKs do not work consistently on women over 40. Some women in their 40s, especially those approaching menopause, have increased levels of LH in their systems at all times, rendering the tests invalid.
5. OPKs don't come cheap. These kits cost between $15 and $50 depending on the brand and number of tests included. Each is good for a single cycle.
Although in most cases, OPKs provide an accurate forecast of your LH surge and subsequent ovulation, they are most effective when used together with other monitoring methods. Along with an OPK, try examining your cervical mucus and charting your basal body temperature -- the term refers to your lowest, or baseline, temperature, and is usually taken first thing in the morning. These methods combined can greatly increase your chances of becoming pregnant.
Sources: American College of Obstetricians and Gynecologists, www.acog.org; Weschler, Toni, Taking Charge of Your Fertility (HarperCollins)
Reviewed by Elizabeth Stein, CNM
All content here, including advice from doctors and other health professionals, should be considered as opinion only. Always seek the direct advice of your own doctor in connection with any questions or issues you may have regarding your own health or the health of others.