Study record · validation · 2019

Nocturnal finger skin temperature in menstrual cycle tracking: ambulatory pilot study using a wearable Oura ring

Maijala A, Kinnunen H, Koskimäki H, Jämsä T, and Kangas M

BMC Women's Health, 19(1), 150 · 2019

Why this study matters to CircaTest

The foundational Oura menstrual cycle / temperature paper. Note: CircaTest article body currently cites this as 'Maijala et al., 2022' which is a year typo — the actual paper is 2019. The retrofit step will correct this.

Abstract

BACKGROUND: Body temperature is a common method in menstrual cycle phase tracking because of its biphasic form. The aim of this pilot study was to assess the applicability of nocturnal finger skin temperature based on a wearable Oura ring to monitor menstrual cycle and predict menstruations and ovulations in real life. METHODS: Volunteer women (n = 22) wore the Oura ring, measured ovulation through urine tests, and kept diaries on menstruations at an average of 114.7 days (SD 20.6). Skin and oral temperatures were compared. Algorithms using skin temperature were tested to predict the start of menstruation and ovulation. RESULTS: Nocturnal skin temperatures and oral temperatures differed between follicular and luteal phases with higher temperatures in the luteal phase (skin: 0.30 °C, SD 0.12; oral: 0.23 °C, SD 0.09; p < 0.001). Correlation between skin and oral temperatures was found using daily temperatures (r = 0.563, p < 0.001). Menstruations were detected with a sensitivity of 71.9-86.5% in window lengths of ±2 to ±4 days. Ovulations were detected with the best-performing algorithm with a sensitivity of 83.3% in fertile window from -3 to +2 days. CONCLUSIONS: Nocturnal skin temperature based on wearable ring showed potential for menstrual cycle monitoring in real life conditions.

Source: PUBMED · Licensed under CC-BY 4.0

Population

Sample size

n = 22

Age

premenopausal women, age not specified

Reference standard

other

22 volunteer women tracked for an average of 114.7 days (SD 20.6) wearing the Oura ring with concurrent urine LH ovulation tests and menstruation diaries.

Devices and metrics

Oura ring (research configuration, predecessor of Gen 3 commercial release)

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Metric	Value	95% CI	Note
Sensitivity	83.3%	—	Ovulation detection sensitivity in fertile window -3 to +2 days.
Sensitivity	86.5%	—	Menstruation detection upper bound (±4 day window).
Sensitivity	71.9%	—	Menstruation detection lower bound (±2 day window).

Cite this study

Maijala A, Kinnunen H, Koskimäki H, Jämsä T, and Kangas M (2019). Nocturnal finger skin temperature in menstrual cycle tracking: ambulatory pilot study using a wearable Oura ring. BMC Women's Health, 19(1), 150. https://doi.org/10.1186/s12905-019-0844-9

AI-assembled record · errors are possible

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Per-device metric values inferred when the abstract reports only an aggregate range
Stage-specific accuracy figures pulled from secondary sources rather than the primary paper
Sample size or population characteristics missing from the abstract
Editorial framing in the curatorial note that overstates the study's actual scope
Year typos and author-name transliteration errors

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Added to the CircaTest meta-analysis on 2026-04-06. How CircaTest evaluates studies →