Ovulation predictor kits (OPKs) are a popular tool used by women who are trying to conceive. They are used to predict when ovulation is likely to occur, which is the period during a woman’s menstrual cycle when an egg is released from the ovaries and is available for fertilisation by sperm. OPKs can be used by women who are trying to conceive naturally or through assisted reproductive technologies, (IVF). OPKs work by detecting a surge in luteinising hormone (LH) levels, which typically occurs one to two days before ovulation. LH is a hormone produced by the pituitary gland that triggers the release of an egg from the ovary. The surge in LH levels can be detected in urine samples using OPKs. OPK’s can be found over the counter in most pharmacies and supermarkets.
To use an OPK, a woman typically begins testing her urine around day 10 of her menstrual cycle, or a few days before she expects to ovulate. The test is performed daily, using a urine sample collected at the same time each day. If the test detects a surge in LH levels, ovulation is likely to occur within the next 12 to 36 hours, and the woman should plan to have intercourse during this time to maximise her chances of conception.
Ovulation predictor kits can be used in conjunction with the fertility awareness method to further improve the accuracy of predicting ovulation, however they are not a requirement to practice FAM (read more about FAM here). Some women may find OPK’s very reassuring while others find them to be an additional source of stress in already stressful fertility journey. At present, research suggests that most women attempting pregnancy enjoy the use of OPK’s without any additional stress or anxiety. This is likely why OPK’s have become so popular in women trying to conceive however each woman’s individual journey is different and women should not been pressured to use OPK’s to confirm ovulation if there are other methods that work better for her. The fertility awareness method involves tracking changes in cervical mucus and basal body temperature, as the main biomarkers of fertility that help to identify the fertile window during a woman’s menstrual cycle. A typical fertile window lasts about 6 days including the day of ovulation itself. Because sperm can survive 5-6 days within the reproductive tract of a woman, pregnancy can occur at any time within the fertile window, however chances of successful conception increase significantly the closer to ovulation, with the highest chance of conception the day before ovulation. By using OPKs to confirm the timing of the LH surge, a woman can further narrow down her fertile window and time sexual intercourse within the period of time that has the highest chance of achieving pregnancy.
OPKs are generally quite accurate in detecting LH but have a success rate of 70-93% in predicting ovulation. It is important to remember that ovulation predictor kits can not actually predict ovulation itself and only detect the presence if LH hormone. How well they do this, depends greatly on the quality of the kit use and how sensitive the OPK is. In most cases, ovulation usually occurs shortly after a surge in LH, but is is possible and very common for LH to be released without ovulation occurring. This is most commonly seen in women with Polycystic Ovarian Syndrome (PCOS) and in some women with irregular cycles. Women with PCOS often have multiple LH surges and so using OPK’s can give multiple positive results without ever confirming ovulation. Stress can cause a similar phenomenon in women with regular cycles and no other known hormone imbalance. This is called a “stress patterned menstrual cycle” and will likely occur to most women several times in their lives. A stress patterned menstrual cycle occurs when the LH signal is sent but ovulation fails to occur due to stress. In this cases, the body attempts ovulation again at a later time meaning that there will be multiple LH surges within a menstrual cycle. Additionally, women with certain medical conditions, such as thyroid disorders or pituitary gland abnormalities, may also have difficulty using OPKs. In some cases, false positives or false negatives can also occur. The accuracy can be affected by a number of factors, including the timing of testing, the quality of the kit, and the individual’s unique hormonal profile so it’s important to follow the instructions carefully and to confirm results with additional testing or monitoring using FAM.
OPK’s can be an accurate and reliable additional tool to helping identify LH surge in women, however OPK’s can not predict ovulation itself. OPK’s are not appropriate for everyone, especially for women with PCOS and irregular cycles. Combining OPK’s with FAM gives a more comprehensive outline of fertility in any given menstrual cycle and can help women get a much more accurate understanding of their fertility on the whole. The choice to use OPK’s alongside FAM is optional and highly dependant on the woman’s preferences.
References:
Leiva, R. A., Bouchard, T. P., Abdullah, S. H., & Ecochard, R. (2017). Urinary Luteinizing Hormone Tests: Which Concentration Threshold Best Predicts Ovulation?. Frontiers in public health, 5, 320. https://doi.org/10.3389/fpubh.2017.00320
O’Connor, K. A., Brindle, E., Miller, R. C., Shofer, J. B., Ferrell, R. J., Klein, N. A., Soules, M. R., Holman, D. J., Mansfield, P. K., & Wood, J. W. (2006). Ovulation detection methods for urinary hormones: precision, daily and intermittent sampling and a combined hierarchical method. Human reproduction (Oxford, England), 21(6), 1442–1452. https://doi.org/10.1093/humrep/dei497
Yeh, P. T., Kennedy, C. E., Van der Poel, S., Matsaseng, T., Bernard, L., & Narasimhan, M. (2019). Should home-based ovulation predictor kits be offered as an additional approach for fertility management for women and couples desiring pregnancy? A systematic review and meta-analysis. BMJ global health, 4(2), e001403. https://doi.org/10.1136/bmjgh-2019-001403
