By: Cara Geoghegan

Editor’s Note: In recent years, the availability of personal devices to track fertility has soared alongside growing demand for such technology. While on the FACTS online elective, Cara Geoghegan wrote this article summarizing a narrative review by Cromack and Walter. [1] Titled “Consumer Wearables and Personal Devices for Tracking the Fertile Window,” it was published in November 2024 in the American Journal of Obstetrics and Gynecology. The review of 23 commercially available devices and wearables marketed to track a woman’s fertile window discusses the scarcity of research backing many of these technologies. Left to wonder whether the market of fertility trackers has seen “more commercialization than innovation,” the authors provide information on potential future cost-effective technologies that may increase their accuracy as well as access to such devices. To learn more about FemTech and its role in fertility awareness, register for Part F of our online CME course.

Introduction

In recent years, a growing interest in health optimization among female consumers has led to an exponential boom in technological innovations in the women’s health sector. Dubbed “FemTech,” these modern devices and apps have become part of a $60 billion industry [2] that continues to skyrocket. Of particular interest to these consumers – predominantly reproductive-age, technologically-proficient women – is investing in tools to understand their ovarian-menstrual cycles better, track their fertile window, and assist in conceiving or avoiding pregnancy. Despite the increasing demand for FemTech products and the rapidly expanding market, research in the field has failed to keep up, thus diminishing the potential impact of these products on the field of women’s health. The narrative review, “Consumer Wearables and Personal Devices for Tracking the Fertile Window” by Cromack et al [1] reviewed the current literature on all devices and wearables used to track the female fertile window to highlight the shortcomings of the current literature as well as areas for future research.

“Despite the increasing demand for FemTech products and the rapidly expanding market, research in the field has failed to keep up, thus diminishing the potential impact of these products on the field of women’s health.”

Methodology

Prior to beginning their review, the authors established clear definitions to refine their literature search. They chose to focus on two categories of new technology marketed specifically to track the fertile window: wearables (designed to assess data points over time through long-term noninvasive contact with the user) and devices (designed to assess data at a specific time-point through short-term contact). The Apple watch and Oura ring are popular modern wearables known for tracking health parameters (temperature, heart rate). The ClearBlue and Inito monitors are popular devices that assess urinary hormone metabolites (LH, estrogen).

“(There are) two categories of new technology … to track the fertile window: wearables (designed to assess data points over time through long-term noninvasive contact with the user) and devices (designed to assess data at a specific time-point through short-term contact).”

PubMed, Scopus, and Google Scholar were used to identify studies in English published from 2000 to 2023 with primary aims to compare effectiveness of the technology to track the fertile window.

Results

A total of 19 articles were included in the final review, which included assessment of 7 wearables and 16 devices available as nonprescription tools for fertile window tracking. All wearable technologies used detection of rise in basal body temperature (BBT) 1-2 days after ovulation as their trackable data point, while most devices detected BBT or urinary hormone metabolites (LH, estradiol, progesterone).

Unfortunately, 9 fertility trackers currently on the market had no publications that met the study’s inclusion criteria. The wearables and devices that were included each had one to four validation studies. Of the 19 articles, 17 were prospective studies, with 13 studies having a sample size of less than 75 women. Other notable findings included limited reporting of race and ethnicity of study participants. Of the 5 studies that did report race, 81.8% of participants were White. Additionally, 11 of the 17 articles only included women with regular cycles.

The reviewers also noted misleading terminology in the studies regarding FDA oversight used in marketing of these products, as well as conflicts of interest among study personnel. Specifically, only 5 of the 19 studies reported no involvement by individuals with stake in the parent company.

Discussion

Cromack and Walter concluded their narrative review with a thorough discussion of these shortcomings, the need for equality in the FemTech world, and a call to action to prioritize innovation over commercialization. As this industry continues to grow, it is critical that investigators independent of the parent company conduct thorough research on a diverse population to determine the potential impact of FemTech to track the fertile window on a woman’s ability to achieve or avoid pregnancy. The Clearblue monitor is the only product that has explicitly published data on live-birth rates associated with use of the device. [3]  As it is likely that women will continue to use these technologies, unbiased studies are needed to assess whether any FemTech products in fact shorten time to pregnancy.*

While there is a wide range of wearables and devices on the market, many of the mainstream technologies are costly. This make them inaccessible for many users and leaves us wondering if women should be spending this much to track their BBT, which they could monitor with an inexpensive thermometer.

Future studies must recruit diverse cohorts. Previous studies have shown some wearable tracking methods are not as accurate in individuals with darker skin tones due to their reliance on photoplethysmography (PPG) to assess data points such as heart rate and oxygen saturation. It is also critical to consider the effectiveness of these technologies in women with irregular cycles and underlying health conditions. Women with irregular cycles and infertility or subfertility may benefit more from fertility window trackers than women with regular cycles and normal fertility. All these women should be represented appropriately in future studies.

“Women with irregular cycles and infertility or subfertility may benefit more from fertility window trackers than women with regular cycles and normal fertility. All these women should be represented appropriately in future studies.”

Many women desire to not only understand their ovarian-menstrual cycle but also use this knowledge to optimize their health and fertility. Their genuine interest has created a profound market for innovative products and groundbreaking research to improve women’s health. Rather than use this momentum to create yet another BBT tracker or urinary hormone device, insightful, unbiased research on existing products is needed as well as collaboration to create new technologies that rely on methods beyond what already exists to help women track their cycles and fertility.

* Editor’s Note: A randomized controlled trial [4] published in 2020 assessed the difference in conception rates in women attempting to conceive without relying on FemTech vs. women who used the app-connected Clearblue ovulation test system to measure urinary LH and an estradiol metabolite. The study findings were promising. The research was funded by the makers of the device.

References

[1] Cromack SC, Walter JR. Consumer wearables and personal devices for tracking the fertile window. Am J Obstet Gynecol. 2024 Nov;231(5):516-523. doi: 10.1016/j.ajog.2024.05.028. Epub 2024 May 18. PMID: 38768799

[2] Stewart C. Femtech market size worldwide from 2021 to 2030: Statista. 2022. Available at: https://www.statista.com/topics/10267/femtech/#topicOverview

[3] Robinson JE, Wakelin M, Ellis JE. Increased pregnancy rate with use of the Clearblue Easy fertility monitor. Fertil Steril 2007;87:329–34.

[4] Johnson S, Stanford JB, Warren G, Bond S, Bench-Capon S, Zinaman MJ. Increased Likelihood of Pregnancy Using an App-Connected Ovulation Test System: A Randomized Controlled Trial. J Womens Health (Larchmt). 2020;29(1):84-90. doi:10.1089/jwh.2019.7850

ABOUT THE AUTHOR

Cara Geoghegan

Cara Geoghegan is a fourth-year medical student at the University of Illinois College of Medicine, Rockford. She completed her undergraduate education at the University of Illinois – Urbana, Champaign.

She is pursuing a career in obstetrics and gynecology and is passionate about providing comprehensive medical care to her future patients.