Health Library
Health Library

Science and research at Flo

Science and research are key to everything we do at Flo. Find out who we partner with, how to work with us, and how we protect the data of people who use Flo.

How we’re supporting and advancing female health

We know that female health lacks research, so we’re doing our part to build a better future. Flo partners with researchers by providing them with aggregated and de-identified reliable medical data without sharing any personal information from the people who use Flo.

How you can work with us

We’re keen to partner with acclaimed scientists, institutions, universities, and research groups (incl. corporate research groups from different business fields) with in-depth subject-matter expertise and proven contributions to global health and well-being.



Key findings:
  • We used data from 16,327 Flo app users to examine the association between menstrual cycle characteristics and sexual motivation.
  • Shorter, more regular cycles predicted small increases in sexual motivation when comparing between women.
  • Shorter cycles predicted greater sexual motivation that month and the next month when comparing within the same women from month to month.
  • This was also linked with more frequent logging of fatigue, insomnia, and food cravings.
  • But changes in sexual motivation did not reliably precede changes in cycle length.
  • Our results suggest that menstrual cycles characteristics and sexual motivation may covary together in ways that reflect changing investments in reproduction.
Key findings:
  • The length of the menstrual cycle and menstrual cycle related symptoms show clear age associated patterns.
  • With increasing age, cycles get shorter and more variable until age 40-44.
  • From this age onwards, periods become longer and more variable, indicating transition toward menopause.
  • The proportion of individuals with irregular cycles was highest in participants aged 51-55 (44.7%), and lowest in the 36-40 age group (28.3%).
  • Frequency of logging of cramps and acne is lower in older participants, while logs of headache, backache, stress and insomnia are higher.
Key findings:
  • Using Flo for three months improved primary outcomes of health literacy, menstrual health awareness, health and wellbeing.
  • It also improved secondary outcomes of feelings of control and
  • management over health, communication about health, menstrual cycle stigma, and fear of unplanned pregnancies.
  • For users with PMS/PMDD, it additionally improves symptom burden and absenteeism from work, and education.
Key findings:
  • There is a lack of standardized tools and regulations for mobile health apps.
  • We evaluated studies that investigated efficacy and effectiveness of mHealth apps, including companies at varied financing stages, with a mix of start-ups (16%), scale-ups (29%), and public companies (39%). A portion of apps were developed by universities or government groups (16%).
  • Most apps (94%) fall into the wellness category, with diet and nutrition, exercise and fitness, mental health, and sleep as the top subcategories.
  • Researchers use a variety of study designs to evaluate apps, the most prevalent being randomized controlled trials (RCT).
  • Lack of diversity in study populations should be addressed to ensure inclusivity and equity. 
Key findings:
  • Women in Ukraine reported increased stress after the Russian-Ukranian conflict started. At the same time, they reported pain less often.
  • After the conflict started, women in Ukraine who reported stress were less likely to report pain. This finding is consistent with the phenomenon of stress-induced analgesia.


Key findings:
  • Single-condition symptom checkers have high levels of agreement with general practitioner classification for endometriosis, uterine fibroids, and PCOS.
  • Sensitivity for the symptom checkers was 81.8% for endometriosis, 84.6% for uterine fibroids, and 100% for PCOS.
  • Specificity was 84.6% for endometriosis, 81.8% for uterine fibroids, and 75% for PCOS.
  • Positive predictive value was reported as 81.8% for endometriosis, 84.6% for uterine fibroids, 80% for PCOS; and negative predictive value was reported as 84.6% for endometriosis, 81.8% for uterine fibroids, and 100% for PCOS.
  • Our paper establishes a robust framework for vignette validation of symptom checkers.
Key findings
  • Most study participants reported improvements in menstrual cycle (88.98%) and pregnancy (84.7%) knowledge from Flo app use.
  • Most of the Flo users (73.5%) who used the app to track their pregnancy believe that Flo helped them get pregnant!
  • The key components of Flo app that helped users improve their cycle knowledge and health are the predictions about periods, fertile days, and ovulation, as well as symptom tracking. Meanwhile, reading articles and watching videos helped users learn more about pregnancy.
  • The strongest improvements in knowledge and health were observed in Premium, frequent, and long-term Flo app users.


Key findings
  • 45.2% of users reported missing, on average, 5.8 days of work due to their cycle.
  • 48.4% do not feel supported by their manager, and 94.6% report no workplace benefit regarding their menstrual cycle.
  • The Flo app helped 88.7% of users to feel prepared and more aware of their bodies and 77.6% to feel supported.
Key findings
  • Cramps were the most common premenstrual symptom.
  • Somatic, gastrointestinal, and negative mood symptoms were most common in the late luteal phase and least common in the midfollicular phase.
  • Negative mood symptoms decreased throughout the follicular phase, while positive mood symptoms were most common in the late follicular phase.
Johns Hopkins School of Medicine and University of Virginia
Key findings
  • Throughout the COVID-19 pandemic, an increase in postpartum depression was found in 36 states of the USA.
  • The increase in postpartum depressive symptoms was greater in the states with fewer deaths from COVID-19 and in the ones where unemployment rates for women were lower in 2020.
Johns Hopkins University
Key findings
  • First-time mothers were more likely to report depressive symptoms than mothers with more children.
  • Depressive symptoms were the highest among young mothers (18-24 years).
  • Mothers of twins reported a higher burden of depressive symptoms than mothers of one child.
Key findings
  • The most common PMS symptoms were food cravings (85.28%), mood swings or anxiety (64.18%), and fatigue (57.3%).
  • Physical premenstrual symptoms increased with age.
  • Premenstrual symptoms regarding anxiety and mood remained similar with age.
  • How much premenstrual symptoms interfere with daily functioning every cycle varies across different countries.


Characterization of Polycystic Ovary Syndrome Among Flo App Users Around the World

Peer-reviewed paper in Reproductive Biology and Endocrinology

Northwestern University
Key findings
  • The most common symptoms of polycystic ovary syndrome (PCOS) vary across different countries.
  • Bloating was the most frequently reported symptom among women with PCOS.
  • Women were at least 3 times more likely to have a PCOS diagnosis if they bloat or have high blood cholesterol and glucose.
  • A PCOS diagnosis is more common in women with a higher BMI.


Key findings
  • PCOS is more common as BMI increases.
  • Having hirsutism increases the probability of PCOS by more than 3 times.
  • The most common symptoms of PCOS vary across different BMI categories.
Adelaide University
Key findings
  • More than 90% of women typically have a cycle length of 21 to 35 days.
  • Less than half — only 40% — of women have a usual cycle length of 27 to 29 days.
  • Length and variation of the cycle are influenced more by women’s age than the body mass index.
  • Less variation and shorter cycles were found in women older than 40.