August 5, 2024

Ovulation Indicators: A Review of Research

By: Brianne Richardson, DO

Director’s Note: Today, we feature a study that explored the various methods of assessing ovulation, ranging from ultrasound to hormones to laparoscopic visualization. The study by Ecochard et al is titled, “Chronological aspects of ultrasonic, hormonal, and other indirect indices of ovulation.” [1] Dr. Brianne Richardson summarized the article while taking the FACTS elective. To learn more about ovulation as a sign of female health, check out the the lecture by Dr. Pilar Vigil in Part D of our online, self-paced CME course, also available for individual purchase here.  View the full CME course syllabus here; up to 160 AAFP-approved CME credits are available to physicians, PAs, nurses, midwives, and other health professionals! Dr. Vigil will also be one of our featured speakers at our upcoming virtual conference on October 18th and 19th, so be sure to register today!

 

Introduction

A woman may desire insight into the timing of her ovulation for many different reasons, such as tracking her overall health and gaining awareness of her fertility. Although laparoscopic visualization is the reference direct method to observe ovulation, it is impractical for routine use for two reasons: advanced training is required to perform the procedure, and it carries inherent risks of anesthesia and surgery. Several less invasive techniques exist, including direct ultrasound detection of day of ovulation (US-DO) and indirect measurement of mid-cycle luteinizing hormone peak (LH-expected date of ovulation). This is a discussion of the research published under the title, “Chronological aspects of ultrasonic, hormonal, and other indirect indices of ovulation,” which compared LH-expected date of ovulation, US-DO, and other indirect methods of predicting timing of ovulation. [1]

“Although laparoscopic visualization is the reference direct method to observe ovulation … several less invasive techniques exist, including direct ultrasound detection of day of ovulation (US-DO) and indirect measurement of mid-cycle luteinizing hormone peak (LH-expected date of ovulation).”

Methodology

The population recruited 12 women from each of 8 natural family planning clinics in France, Italy, Germany, Belgium, and Spain. Subjects were women aged 18-45, normally fertile, and cycling. Interestingly, runners, breastfeeding women, and postpartum mothers were excluded. In total, 107 women were included in the study. Data included urinary measurements of LH, follicle-stimulating hormone (FSH), oestrone-3-glucuronide (estrogen), and pregnanediol-3a-glucuronide (progesterone). Transvaginal ultrasound imaging of the ovaries, basal body temperature (BBT), and cervical mucus quality were also recorded. Measured outcomes included time delay between LH-expected date of ovulation, US-DO, and other indirect predictors of ovulation.

Results

Of 326 observed cycles, ultrasound imaging confirmed ovulation in 283 cycles (86%). LH-expected date of ovulation was identified in 273 of the 283 ultrasound-confirmed ovulatory cycles. LH-expected date of ovulation occurred within 1 day of US-DO in 67.6% of cycles. As estimated by LH-expected date of ovulation compared to US-DO, premature ovulation and late ovulation occur in 10% and 23% cycles, respectively. Occurring within one day of US-DO in 72% of the 283 cycles, cervical mucus-expected date of ovulation, LH initial rise (IR), and ratio-expected date of ovulation (calculated from ratio of urinary estrogen to progesterone) gleaned standard deviations of 1.6, 2.2, and 2.4 days from US-DO, respectively.

Discussion

During the FACTS webinar, The Female Cycle as the Fifth Vital Sign, we learned that knowledge about one’s body empowers decision making. With fertility awareness-based methods (FABMs), women can monitor their healthy cycles, identify symptoms of disease, and make informed decisions about family planning. [2] Rather than focusing on the menses phase, emphasis should be placed on ovulation as part of a continuum that occurs in healthy women throughout their lifetime. This study examined the utility of tracking cervical mucus, LH surge and urinary hormone measurements to identify the estimated day of ovulation and demonstrated ovulation occurs within 1.6-2.4 days of US-DO based on these biomarkers.

Happy couple taking selfie showing the results of pregnancy test sitting on the sofa at home

“This study examined the utility of tracking cervical mucus, LH surge and urinary hormone measurements to identify the estimated day of ovulation and demonstrated ovulation occurs within 1.6-2.4 days of US-DO based on these biomarkers.”

The female cycle consists of menses, a follicular phase rich in estrogen, an LH surge affecting an unruptured follicle, ovulation of said follicle, a luteal phase rich in progesterone, and a decrease in progesterone that results in menses and completes the cycle. Deviation from this cycle, including anovulation, represents a deviation from healthy physiology and may suggest pathology. Women can use knowledge about ovulation and their menstrual cycles to restore fertility and plan their family. [2][3][4] For all these reasons, women benefit from the ability to predict ovulation reliably during each cycle. The reviewed study presents data analysis showing the accuracy and reliability of various FABMs to predict ovulation.

Strengths of this study include a large sample size, strict adherence to criterion for detection of US-DO by ultrasound investigation centers, and comparison of ultrasonographic, clinical (cervical mucus and BBT), and hormonal (urinary LH, FSH, estrogen, and progesterone) measures. Additionally, this research was conducted in family planning centers, suggesting protocols can be developed for practical use in this setting. The financial, emotional, and time commitments required to determine US-DO may limit the method’s applicability to highly motivated women and/or women with surmountable barriers to healthcare access. Affordable, reliable methods that can be easily used in the privacy of one’s home should be prioritized in future research.

One of the most applicable insights from this study is the accuracy of US-DO, suggesting studies of alternative methods to predict ovulation should be compared to US-DO. LH initial rise and peak, determined via relatively inexpensive home tests, accurately predict ovulation in 77% and 67% of cycles, and can be recommended to predict ovulation in cases where an individual is attempting pregnancy. Despite their reliability regarding prediction of ovulation, estrogen, progesterone, and FSH home tests are expensive. More research and development could be conducted to make these prediction methods more accessible. Basal body temperature nadir and rise often occur more than 2 days from US-DO, making BBT monitoring a less reliable method to predict ovulation. Cervical mucus peak symptoms occur closer to US-DO and have advantages over self-monitoring of BBT, making cervical mucus peak symptom monitoring a convenient and moderately reliable method to detect ovulation.

“LH initial rise and peak, determined via relatively inexpensive home tests, accurately predict ovulation in 77% and 67% of cycles, and can be recommended to predict ovulation in cases where an individual is attempting pregnancy.”

Questions remain regarding the methods and conclusions drawn from this study. Further research should be conducted in populations excluded from this study, including runners, postpartum women, breastfeeding women, and those with abnormal cycles or issues with fertility. Although not inherent to running, training overload can result in decreased energy availability and suppressed ovarian function in female runners. However, increased energy intake could prevent suppression of ovarian function, and further research may be necessary to elucidate reasoning for exclusion of runners from this study. [5]

References

[1] Ecochard R, Boehringer H, Rabilloud M, Marret H. Chronological aspects of ultrasonic, hormonal, and other indirect indices of ovulation. BJOG. 2001;108(8):822-829. doi:10.1111/j.1471-0528.2001.00194.
[2] Vacca, Kim. The Female Cycle as the Fifth Vital Sign. Lecture accessed via FACTS about Fertility: Fertility Awareness for Women’s Health lecture series.
[3] Duane M, Stanford JB, Porucznik CA, Vigil P. Fertility Awareness-Based Methods for Women’s Health and Family Planning. Front Med (Lausanne). 2022;9:858977. Published 2022 May 24. doi:10.3389/fmed.2022.858977
[4] Brown JB. Types of ovarian activity in women and their significance: the continuum (a reinterpretation of early findings). Hum Reprod Update. 2011;17(2):141-158. doi:10.1093/humupd/dmq040
[5] Schaal K, VanLoan MD, Hausswirth C, Casazza GA. Decreased energy availability during training overload is associated with non-functional overreaching and suppressed ovarian function in female runners. Appl Physiol Nutr Metab. 2021;46(10):1179-1188. doi:10.1139/apnm-2020-0880

ABOUT THE AUTHOR

Brianne Richardson, DO

Brianne Richardson, DO is a first-year resident at the University of Wyoming Family Medicine Residency in Casper, Wyoming. She completed her undergraduate studies in human nutrition, foods, and exercise at Virginia Tech, and earned her medical degree from the Philadelphia College of Osteopathic Medicine in Suwanee, Georgia. Dr. Richardson aims to practice full-scope family medicine at a critical access hospital in the Mountain West. She enrolled in the FACTS elective to deepen her understanding of women’s physiology and to empower women to make informed health and reproductive decisions through education.


 

Check out part D of the FACTS CME CourseMedical Applications of FABMsto learn more about ovulation as a sign of health from Dr. Pilar Vigil!

 

 

Wearables and Devices to Track the Fertile Window: A Review

By: Cara Geoghegan Editor’s Note: In recent years, the availability of personal devices to track fertility has soared alongside growing

FACTS Conference Speaker Highlight: Anita Showalter, DO, FACOOG

Editor’s Note: We are honored to highlight Dr. Anita Showalter, one of our keynote speakers for the upcoming FACTS Annual

FSH Sensitization in Premature Ovarian Failure Provides Hope of Natural Conception

Editor’s Note: From time to time, research goes beyond collecting data and information to inspire hope for the future. The