By: Divya Venkat
Editor’s Note: Divya Venkat was a fourth-year medical student on the FACTS elective when she summarized the research article [1] we feature this week by Drs. Paula Adams Hillard and Marija Wheeler. Published in the Journal of Pediatric & Adolescent Gynecology in 2017, its title is “Data from a Menstrual Cycle Tracking App Informs Our Knowledge of the Menstrual Cycle in Adolescents and Young Adults.” As in ACOG’s 2015 statement, [2] the authors present the female cycle as the 5th vital sign and an important marker of health among adolescents. They also recognize that disruptions in the female cycle (the ovulatory-menstrual cycle)* may signal the presence of common medical conditions among adolescent girls and adult women, highlighting the importance of tracking cycle data.
Introduction
Ovulatory-menstrual cycle characteristics play an important role in reproductive health and provide insights into the wellbeing of adolescents and young adults. Historically, research on menstrual cycles has been limited by small sample sizes and sparse geographic representation. Newer period-tracking apps, such as Clue, offer access to a more diverse, vast collection of data, potentially aiding our understanding of menstrual cycles. The study by Hillard and Wheeler [1] summarized below analyzed menstrual cycle data from Clue users to consider what constitutes a “normal” cycle in adolescents and young adults, paying special attention to how cycle lengths vary by age.
“Ovulatory-menstrual cycle characteristics play an important role in reproductive health and provide insights into the wellbeing of adolescents and young adults.”
Clue is an app that allows users to track their monthly cycle, including symptoms, period length, and cycle length. It can also track mucus or fluid secretions, bleeding amount, pain, sleep, energy, cravings, mood, and more.
Methodology
This study analyzed ovulatory-menstrual cycle data from Clue that was de-identified, meaning all personal and identifying information was removed. The dataset analyzed includes information from over 816,000 adolescents and young adults who tracked more than 5 million cycles. Data from users on hormonal birth control were excluded because hormonal contraception can alter menstrual patterns, and the researchers sought to gather data from natural cycles. Study data were grouped by age; key statistical measures (e.g., mean, median, 5th and 95th percentiles of cycle lengths) were calculated to assess cycle length variations by age group.
Results
The study showed several patterns in menstrual cycle lengths:
- The mean cycle length for younger adolescents aged 9-11 was 35 days, compared to 32 days for older adolescents and young adults (15+ years). This 32-day average was similar to women in their 20s and 30s.
- For adolescents aged 9-13 years, mean cycle lengths ranged from 33 to 36 days.
- On average, the youngest age group displayed more variability in cycle lengths; those 15 years and older had a more stable length of 32 days.
- The median cycle length for the 9-11 age group was similar to the older groups but had a wider distribution, reflecting greater fluctuation in their cycles.
When compared to studies such as Treloar et al’s study from 1967, the 95th percentile of cycle lengths in the Clue dataset was longer than in prior research. This suggests modern-day menstrual cycles may be longer, on average, than those from previous generations. This could be due to environmental factors, changes in diet and nutrition, other lifestyle changes, stress, and more.
“On average, the youngest age group displayed more variability in cycle lengths … (and the data) suggests modern-day menstrual cycles may be longer, on average, than those from previous generations.”
Discussion
This study gives medical professionals insight into key trends in menstrual cycles in adolescents and young adults, which can be useful in clinical practice. A main takeaway is that younger adolescents tend to have longer, less predictable cycles due to hormonal fluctuations during early puberty. As they reach 15 years and older, their cycles become more regular and stable. This aligns with previous research on this topic, and this study’s large sample size further validates those earlier results.
A strength of this study is its large, diverse sample size because it offers a broader view of menstrual patterns among thousands of women. However, a study limitation is that the Clue app does not consider gynecologic age (years since menarche), which could affect the results. The study also excludes women on hormonal birth control, limiting its applicability to that group.
The study findings are especially helpful for women who use fertility awareness-based methods (FABMs) such as the Creighton Model, the SymptoThermal Method, and the Billings Ovulation Method, which monitor biomarkers such as menstrual bleeding and cervical mucus. By establishing what’s considered “normal,” this study gives FABM users a clearer understanding of their cycles and how to manage their reproductive health better.
Apps that track menstrual data and symptoms may offer women an empowering way to learn more about their bodies, particularly for those who learn to chart their cycles with FABMs. They can help pinpoint the fertile window for those trying to get pregnant and even identify early signs of common health conditions such as polycystic ovary syndrome (PCOS), endometriosis, fibroids, and more. Coupled with charting, these apps can serve as an early warning system for irregular cycles and hormonal imbalances.
Additionally, defining what’s typical for menstrual cycles means medical professionals can avoid unnecessary testing. For instance, longer cycles in younger adolescents are normal and common; it is important to recognize the difference between natural variation and something that may require medical attention.
“Apps that track menstrual data and symptoms may offer women an empowering way to learn more about their bodies, particularly for those who learn to chart their cycles with FABMs. … (and) defining what’s typical for menstrual cycles means medical professionals can avoid unnecessary testing.”
Menstrual tracking apps may give women more control over their health care by providing the data they need to make informed decisions as they work with their physicians. These tools can be especially useful to manage chronic conditions, track symptoms, and understand fertility patterns, ultimately leading to better reproductive health management.
Conclusion
This study highlights how important it is to understand what a normal ovulatory-menstrual cycle looks like for all age groups and populations — not only to diagnose common medical conditions but also to raise awareness around healthy cycles, hormones, and fertility. Period tracking apps can empower women to better understand their bodies, giving them more control over their health. For medical professionals, this research shows how important it is to have large-scale data to define what constitutes “normal.” It may also help them make more accurate, timely diagnoses when it comes to issues related to the ovulatory-menstrual cycle. As digital tools for reproductive health continue to grow in popularity, this approach could play an impactful role to support women’s health and fertility awareness worldwide.
Editor’s Note: In recent years, the field of women’s health and fertility has seen an explosion of digital tech (FemTech), including numerous apps and wearable devices. When using menstrual tracking apps and other FemTech, due diligence is an essential step to ensure these tools have solid evidence behind their stated purpose. A research article published in 2016 [3] provides ratings of apps designed to help couples avoid pregnancy; a printable summary of the study findings can be accessed here. To learn more about FemTech, follow the link to relevant studies summarized by students on the FACTS fertility awareness elective and register for Part F of our online CME elective: Fertility Awareness and Fem Tech. For a summary of ACOG’s statement on the menstrual cycle* as a 5th vital sign, read ACOG Supports Fertility Awareness Education.
*At FACTS About Fertility, we often refer to the “menstrual cycle” as the ovulatory-menstrual cycle to emphasize that ovulation, not menstruation, is the 5th vital sign of health and the main event when it comes to the female cycle!
References
[1] Adams Hillard, Paula J and Vlajic Wheeler, Marija. Data from a menstrual cycle tracking app informs our knowledge of the menstrual cycle in adolescents and young adults. J Pediatr Adolesc Gynecol. 2017;30(2):269-270.
[2] Committee Opinion No. 651 “Menstruation in Girls and Adolescents: Using the Menstrual Cycle as a Vital Sign.” Obstetrics & Gynecology. 2015;126(6). doi:10.1097/aog.0000000000001215
[3] Duane M, Contreras A, Jensen ET, White A. The Performance of Fertility Awareness-based Method Apps Marketed to Avoid Pregnancy. J Am Board Fam Med. 2016;29(4):508-511. doi:10.3122/jabfm.2016.04.160022
ABOUT THE AUTHOR
Divya Venkat
Divya Venkat is a fourth-year medical student at Kansas City University College of Osteopathic Medicine in Kansas City, MO. She completed her undergraduate education at the NC State University in Raleigh, NC. She plans to pursue residency in obstetrics and gynecology and is interested in women’s health, mentorship, and advocacy. She enrolled in the FACTS elective to better understand natural family planning methods and ways to share them with future patients so they feel more empowered over their health and reproductive decisions.
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 membership@FACTSaboutFertility.org.
