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Advancing science and research for female health
On a global level, female health lacks research. That’s why it underpins everything we do at Flo. Together with our scientific advisory board and collaborators, we’re working to build a better future for female health through innovative research studies.
Our science team is committed to finding new ways to support groundbreaking app features and addressing the gaps in female health science.
20+
scientists
scientists
working to advance female health
22+
million
million
research participants
15+
members
members
of Flo's scientific advisory board
The latest publications from Flo
2026
Published in npj Digital Medicine
Key findings
- Digital symptom checkers are increasingly used to support early symptom recognition and care-seeking, yet evidence on their cost-effectiveness remains limited.
- We conducted an economic evaluation of a digital symptom checker for endometriosis, as a case study. We developed a Markov decision process model to compare the digital symptom checker with the standard of care from a societal perspective.
- Over a 40-year horizon, the outcomes were:
- reduction in diagnostic delay by 4.36 years
- cost saving of $5,196.22 per patient
- gain of 0.049 quality-adjusted life years (QALYs) per person (approx. 18 extra days of healthy life)
- net monetary benefit of $10,089.00 at a $100,000/QALY threshold
- Although this is a case study, it serves as an example for symptom checkers for other conditions characterized by prolonged diagnostic delays, stigma, high societal costs, and low care-seeking rates.
Key findings
- This cross-sectional study investigated levels of knowledge of possible perimenopause symptoms among Flo app users 18+ and symptom experiences among Flo app users 35+
- The top recognized of 26 possible perimenopause symptoms were: hot flashes (71%), sleep problems (68%), weight gain (65%)
- Participants from the United Kingdom recognized the most symptoms, followed by Ireland and Australia. Participants from Nigeria, France, and Venezuela recognized the least symptoms.
- Among women 35+ who self-identified as being in perimenopause, the most common symptoms were exhaustion (95%), fatigue (93%), irritability (91%).
2025
Peer-reviewed paper in BMJ Public Health
Key findings
- Low levels of basic menstrual health knowledge remain a significant global challenge, and this has been linked with reproductive health concerns, societal stigma, and social exclusion.
- This was a longitudinal study with 276 individuals in the pre-post sample and 6,379 individuals in a matched, cross-sectional sample, recruited from 52 low- and middle-income countries.
- After at least three months of using the Flo app, we observed significant positive changes in the matched sample:
- menstrual health knowledge increased by nearly 19%
- menstrual health awareness increased by 9%
- communication confidence was up by 4%
- STI awareness was up by nearly 2%
- importantly, there was an 8% reduction in menstrual stigma
- Our findings were largely consistent in the pre-post design, but in this part of the study, we also saw:
- improvements in quality of life and bodily appreciation by nearly 4%
- a reduction in menstrual impact by nearly 7%
- Using mediation analysis in the matched sample, we found that higher menstrual health knowledge after using the app was a significant driving factor for improvements in other outcomes.
Perimenopause symptoms, severity, and healthcare seeking in women in the US
Peer-reviewed paper in npj Women’s Health
Key findings
- We conducted a cross-sectional survey of 4,432 women aged 30 and over in the US to understand healthcare seeking for perimenopause, symptoms and symptom burden, and the impact of age on these.
- Healthcare seeking for perimenopause was highest among women aged 56 and over (51.5%), but 30% of those visiting a doctor about symptoms were under 46.
- Total symptom burden was highest in women aged 51 to 55 and lowest in women aged 30 to 35.
- However, significant proportions of women in all age groups reported moderate to severe symptom burden including 55.4% of women aged 30 to 35 and 64.3% of women aged 36 to 40.
- The types of symptoms that women most likely experience varied by age with psychological and mood symptoms more prevalent in women aged 41 to 45 and vasomotor and other physical symptoms more prevalent in women aged 51 to 55.
Female sexual response among Flo app users in the United States
Peer-reviewed paper in npj Women’s Health
Key findings
- Sexual problems are commonplace and impact an estimated 41% of females in the United States.
- In a survey of 2,392 Flo app users in the US, we used the scientifically validated female sexual function index 6 (FSFI-6) to measure female sexual response.
- Those who were using Flo’s Trying To Conceive mode and those who were logging sex events more often had higher FSFI-6 scores, indicating better sexual response.
- Conversely, women with a body mass index below 18 (underweight) and those who had at least one chronic health condition queried in the survey had low FSFI-6 scores.
- Study participants who were 35 and over reported higher orgasm frequency, less pain during sex, and lower satisfaction with their overall sex life than women under 35, although the overall FSFI-6 scores were comparable.
2024
Peer-reviewed paper in JMIR Formative Research
Key findings
- The most prevalent self-reported symptoms were fatigue, feeling anxious, high BMI for PCOS, very regular lower abdominal pain, fatigue, and referred lower back pain for endometriosis, and fatigue, bloating, and changing sanitary protection often for uterine fibroids.
- The most predictive self-reported symptoms were symptoms of anovulation, amenorrhea, and hyperandrogenism for PCOS and symptoms related to abdominal pain and the effect pain has on life, bleeding, and fertility complications for endometriosis and uterine fibroids.
- Symptom checker accuracy was 78% for PCOS, 73% for endometriosis, and 75% for uterine fibroids.
Peer-reviewed paper in Scientific Reports
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.
Chronicling menstrual cycle patterns across the reproductive lifespan with real world data
Peer-reviewed paper in Scientific Reports
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.
Peer-reviewed paper in JMIR mHealth and uHealth
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.
Peer-reviewed paper, in press in BMC Digital Health
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.
Peer-reviewed paper in npj Mental Health Research
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.
2023
Peer-reviewed paper in JMIR mHealth and uHealth
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.
Peer-reviewed paper in JMIR mHealth and uHealth
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.
2022
Peer-reviewed paper in Digital Health
University of Virginia
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.
Peer-reviewed paper in Journal of Psychiatric Research
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.
Risk Factors Associated with Postpartum Depressive Symptoms: A Multinational Study
Peer-reviewed paper in Journal of Affective Disorders
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.
Premenstrual Symptoms Across the Lifespan in an International Sample: Data From a Mobile Application
Peer-reviewed paper in Archives of Women’s Mental Health
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.
2021
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.
2020
Relationship Between BMI and PCOS Symptoms Among Flo App Users in the United States
Poster presentations
Northwestern University
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.
Peer-reviewed paper in Journal of Medical Internet Research
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.
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