By Kenna Decker, DO
Editor’s Note: Dr. Kenna Decker, DO, wrote this article during her fourth year at the Chicago College of Osteopathic Medicine as part of the FACTS elective. In this review, she discusses the findings of Marshall et al. on the Billings Ovulation Method and cervical mucus observations as predictors of conception. Her summary highlights the value of fertility literacy in women’s health and acknowledges what women consider when choosing a fertility awareness-based method (FABM) that best aligns with their health needs, lifestyle, and reproductive goals. If you are new to this field and want to learn more about how FABMs can be used to help achieve pregnancy, please check out one of our introductory webinars here.
Introduction
The diagnosis of infertility is typically made once patients have not been able to conceive after one year of regular sexual intercourse. This timeline is utilized so that there is a benchmark for when to start investigating the causes of infertility. Prompt evaluation of infertility is warranted, as the probability of natural conception decreases with advancing age and with increasing duration of infertility beyond one year.
“Prompt evaluation of infertility is warranted, as the probability of natural conception decreases with advancing age.”
This study seeks to analyze fertility potential with cervical mucus quality as its fertility marker. The Billings Ovulation Method is a fertility awareness-based method (FABM) in which individuals are taught to analyze their cervical mucus to understand their fertility patterns.[6] Individuals can then utilize this knowledge to match intimacy habits with their fertility goals, whether that be avoiding or achieving pregnancy. The Billings method relies on daily data collection based on vulvar sensation and quality of cervical mucus. As hormones rise and fall throughout the ovulatory-menstrual cycle, there will be an observable change in the quality and quantity of cervical mucus. For example, as estrogen rises throughout the follicular phase, the cervical crypts produce a lubricative, slippery mucus—which can be noted through vulvar sensation. This mucus will then disappear and be replaced by a sensation of dryness, which corresponds with the rise in progesterone following ovulation during the luteal phase of the cycle.[3]
“The Billings Ovulation Method is a fertility awareness-based method (FABM) in which individuals are taught to analyze their cervical mucus to understand their own fertility patterns … based on vulvar sensation and quality of cervical mucus.”
It is well established that fertility-focused intercourse during the fertile window is strongly correlated with increased probability of conception.[5] The Billings method can aid women in identifying their own fertile window based on mucus observations, which provide real-time data about themselves rather than making best guesses based on population patterns, such as the common practice of calling cycle day 14 the day of ovulation.[4] This is particularly useful in individuals who have irregular cycles as they may ovulate on different days from one cycle to the next.[1]
The highest probability of conception occurs when couples have intercourse on the day with the most fertile-type mucus.[7] This may occur one to two days before the peak day—defined as the last day of mucus before the switch to the dry sensation fueled by progesterone.[8] This knowledge allows couples to time intercourse based on their reproductive goals. For those trying to conceive, this knowledge is very useful. However, many women are unaware that cervical mucus is a sign of fertility.[2] These instructions can be provided to patients in person or via telehealth. There are paper and online options for charting the data collected with the Billings method. The method is readily available regardless of location, is cost-effective, and is relatively simple to understand across different backgrounds and education levels.
The study investigated whether fertility biomarkers identified through the Billings method of charting were associated with successful conception, and it evaluated the method’s utility for couples attempting to conceive.
Method
Participants were recruited from a group of women who attended Billings Ovulation Method clinics throughout Australia between 1999 and 2003. Each participant wanted to conceive and was willing to utilize the method. Each participant was then followed for two years or until they became pregnant.[6]
Participants were instructed to follow the Billings method, which included keeping a daily record of vulvar sensation, any observations regarding the quality of their cervical mucus, and instances of intercourse.[2] Participants were provided with instructions on their patterns of fertility based on mucus quality and the corresponding hormone changes.
De-identified data were collected regarding mucus patterns, peak symptoms, bleeding, luteal phase length, and timing of intercourse. A questionnaire was conducted after which each participant’s response was blinded to whether pregnancy was achieved and classified according to fertility symptoms. For statistical analysis, participants were grouped according to how long they had been trying to conceive, normal fertility (<12 months), infertility (>12 months), and prolonged infertility (>24 months).[6]
Results
The charts of 384 qualifying women were available for analysis and included in the study. From this group, 62.5% achieved pregnancy within the 24-month study period and 20.8% did not. The remaining 16.7% of charts did not provide data as to whether the women became pregnant during the study and were thus classified as “unknown.”[6]
Among participants who noted peak type mucus, 72.3% achieved pregnancy during the study period; this was found to be independently associated with duration of infertility and age group. Symptoms of fertility according to the Billings method criteria were associated with a 30% increase in pregnancy rates when compared to those who did not note adequate fertile-type mucus. The study provides more specific data on the percentage of patients who achieved pregnancy with and without favorable fertility symptoms within each age and fertility group. Evidence of timing intercourse at peak fertility was found to be statistically significant. Additionally, the study noted mucus symptoms of peak fertility being associated with a much shorter time to conception compared to those with absent mucus symptoms: 77.1% of pregnancies were achieved within the first six months for those with favorable mucus.
Discussion
There are several takeaways from this study. First, fertile-type mucus can be an important diagnostic tool for stratifying pregnancy potential. It is common for women to question whether their timeline is normal, even within the first few months of trying to conceive. If women and their physicians could have informed discussions regarding their individual fertility potential based on mucus quality, age and fertility group, it would direct decisions regarding the timing of infertility work ups.
Another takeaway is how counseling patients and informing them that 92.5% of pregnancies among women with high-quality cervical mucus occur within the first year of fertility-focused intercourse—and that 77.1% occur within the first six months—may provide reassurance, reduce anxiety, and encourage continued patience before pursuing further evaluation. For women with unfavorable mucus patterns, it may be worthwhile to begin a fertility workup much sooner, even if they have only been trying to conceive for a few months, because we know that only 44% of women with poor mucus quality were able to conceive within the two-year study period. Rather than wasting precious time, especially when age may be a factor, it could be prudent to start the process much earlier than the one year typically required for an infertility diagnosis. Having a marker of fertility that can provide real-time data without costing patients a dime is a valuable resource and should be utilized more widely.
“Counseling patients that 92.5% of pregnancies among women with high-quality cervical mucus occur within the first year of fertility-focused intercourse—and that 77.1% occur within the first six months—may provide reassurance, reduce anxiety, and encourage continued patience before pursuing further evaluation.”
An additional note regarding the potential for practical application of this study centers on the use of the Billings method. This method is well tolerated compared to other methods that require women to touch their cervical mucus or purchase equipment, such as thermometers or urinary hormone monitors. This method is also easily understood and can be taught to a wide variety of individuals regardless of background, education level, and economic status. FABMs in general also work well for those who may be unwilling to utilize other forms of family planning due to health or religious reasons. Patients should be able to obtain this information from their primary care physician and partner alongside them to better understand their fertility without having to pursue specialist care.
Prior to this elective, I understood FABMs as potential methods of birth control, but I did not know how useful these methods were for truly understanding one’s own fertility and how they can be utilized very effectively when trying to conceive through observations of cervical mucus.
Although women often learn that vaginal discharge represents a normal physiologic finding, they rarely receive education about how changing cervical fluid patterns correspond with the ovulatory-menstrual cycle and fertility. Expanding access to this knowledge through health education courses, primary care practices, and reproductive health counseling could empower women with a stronger understanding of their reproductive health.
“A solid foundation in the ovulatory-menstrual cycle and fertility benefits all women, regardless of whether they plan to achieve pregnancy, avoid pregnancy, or simply gain a deeper understanding of their own bodies.”
One limitation of this study is that the Billings method relies on a subjective interpretation of mucus quality, and some women said they struggled with this method in comparison to methods with more objective measures. It may be worth repeating the study with other FABM methods. Another limitation is the amount of incomplete data analyzed that provide unknown outcomes for some of the participants. It may be that pregnancy rates were higher within the two-year time period, but that data was incomplete and thus skews the fertility rates falsely low.
It would be interesting to see the study repeated with a larger sample size. It would also be useful to analyze data based on the different reasons for infertility. Those with and without formal diagnoses were included in this study regardless of whether they were being treated for the reason behind their infertility. These confounding variables would be useful to note and investigate more specifically. I would also like to see a study in which the women with unfavorable mucus were treated for that symptom and followed up with to track improvement of mucus quality and pregnancy after treatment.
This study and the FACTS elective course demonstrated how an accurate fertility chart can become an invaluable diagnostic tool in complex clinical cases. Women deserve education about the full spectrum of reproductive health options so they can make informed decisions regarding their care. FABMs warrant discussion because of their effectiveness for both preventing and achieving pregnancy, as well as their ability to help women recognize and interpret the signs of their own fertility.
References
[1] Billings, J. J. (1991). The validation of the Billings ovulation method by laboratory research and field trials. Acta Europaea Fertilitatis, 22 (1), 9-15.
[2] Billings, E., & Westmore, A. (2011). The Billings Method: Using the body’s natural signal of fertility to achieve or avoid pregnancy. Anne O’Donovan.
[3] Brown, J. B. (2011). Types of ovarian activity in women and their significance: the continuum (a reinterpretation of early findings). Human reproduction update, 17 (2), 141-158.
[4] Ecochard, R., Duterque, O., Leiva, R., Bouchard, T., & Vigil, P. (2015). Self-identification of the clinical fertile window and the ovulation period. Fertility and Sterility, 103 (5), 1319-1325.
[5] Evans-Hoeker, E., Pritchard, D. A., Long, D. L., Herring, A. H., Stanford, J. B., & Steiner, A. Z. (2013). Cervical mucus monitoring prevalence and associated fecundability in women trying to conceive. Fertility and sterility, 100 (4), 1033-1038.
[6] Marshell, M., Corkill, M., Whitty, M., Thomas, A., & Turner, J. (2021). Stratification of fertility potential according to cervical mucus symptoms: achieving pregnancy in fertile and infertile couples. Human Fertility, 24 (5), 353-359.
[7] Scarpa, B., Dunson, D. B., & Colombo, B. (2006). Cervical mucus secretions on the day of intercourse: an accurate marker of highly fertile days. European journal of obstetrics & gynecology and reproductive biology, 125 (1), 72-78.
[8] Wilcox, A.J., Weinberg, C.R., & Baird, D.D. (1995). Timing of Sexual Intercourse in relation to ovulation. N Engl J Med, 333(23):1517-1521.
ABOUT THE AUTHOR
Kenna Decker, DO, is a first-year Family Medicine resident at the Clarkson Family Medicine Residency Program in Omaha, Nebraska. A graduate of the Chicago College of Osteopathic Medicine, she has a strong interest in women’s health and comprehensive primary care.
Inspired by what you read?
You can support the ongoing work of FACTS here. To connect with a member of our team, please email development@FACTSaboutFertility.org. Interested in becoming an individual or organizational member? You can learn more and register here. To discuss with a member of our team, please email members@FACTSaboutFertility.org.
