How to measure basal body temperature: chart and thermometer

Measuring basal body temperature is often the first thing couples try when getting pregnant does not happen right away: a thermometer on the nightstand, one reading every morning, and after a few weeks, a chart. According to the US professional society ASRM, the method is inexpensive but often unreliable (ASRM 2021).

Before you start, you should know what the chart can deliver. It shows ovulation only after it has already happened. The most fertile days come before it.

Here you will learn how to measure correctly, how to read your chart with the 3-over-6 rule, what distorted readings mean, and why international guidelines do not recommend the chart for confirming ovulation. Includes an example chart as a table and a template to fill in.

What basal body temperature shows

Basal body temperature is your body temperature at rest, measured in the morning before you get up. The British professional society FSRH defines it as the temperature before getting up after at least 3 hours of rest (FSRH 2015).

After ovulation, the hormone progesterone raises basal body temperature, and it stays elevated until your next period (FSRH 2015). The rise is small: only a few tenths of a degree, roughly 0.4 to 0.9°F (0.2 to 0.5°C) depending on the source (WHO 2022, frauenaerzte-im-netz.de). Cycles with ovulation therefore usually show a biphasic chart, with a low phase in the first half of the cycle and a high phase in the second half (ASRM 2021).

Why the chart only works in hindsight

Temperature usually rises 1 to 2 days after ovulation, sometimes on the day itself (familienplanung.de). Measured against the peak of luteinizing hormone (LH) in the blood, which announces ovulation, the calculated temperature rise came on average 2.4 days later (± 1.5 days) in a small validation study of 24 cycles, and up to 4.1 days later depending on the evaluation method. The authors consider charts read by eye alone unreliable (Prior 1990).

The fertile time, however, comes before that. The fertile window spans 6 days: the 5 days before ovulation and the day of ovulation (familienplanung.de). According to ACOG, the most fertile days are the 2 to 3 days before the temperature rise. More than 6 days before the rise and more than 2 days after it, the chance of conception was negligible in one study (FSRH 2015).

So when your chart rises, the most fertile time of that cycle is usually already over. Detecting ovulation after the fact is easier than predicting it (familienplanung.de).

How to measure basal body temperature: step by step

The rules are simple; sticking with them is the harder part. Here is how to go about it:

1. Have your thermometer ready. In the evening, put a digital thermometer that measures to two decimal places within reach next to your bed (IQWiG 2025).
2. Measure right after waking up. While still lying down, before you get up and before you go to the bathroom (IQWiG 2025).
3. Always at the same site. Vaginally or rectally (IQWiG 2025), and according to the S2k guideline orally as well (AWMF 015-095). Stick with one measuring site, because temperature differs depending on the body site: Orally measured values are on average about 0.4°F (0.2°C) lower than rectally measured ones (frauenaerzte-im-netz.de). Measuring under the armpit is too inaccurate.
4. Rest beforehand. According to the BVF and DGGG portal frauenaerzte-im-netz.de, you should have slept or rested for 1 hour before measuring, and 6 hours of sleep are not necessary. FSRH, by contrast, defines basal body temperature after at least 3 hours of rest. The recommendations therefore differ. A night that is too short or disrupted can raise the temperature (IQWiG 2025).
5. Time of day: ideally the same. Whether you have to measure at the same time every day is viewed differently by the sources. IQWiG advises always measuring at the same time (IQWiG 2025). According to the German-language S2k guideline, this is no longer necessary (AWMF 015-095). Highly irregular sleep-wake times make the values jumpy (Henry 2024).
6. Write it down right away. Enter the value immediately, on paper or in an app (IQWiG 2025). Note anything unusual: a short night, alcohol the evening before, a cold.
7. Measure through the whole cycle. The easiest way is to start on the first day of your period (cycle day 1). For the evaluation, you need at least six values before the rise.

Reading your basal body temperature chart: the 3-over-6 rule

A single higher value does not tell you anything yet; it can also come from a short night or an infection (IQWiG 2025). Only the pattern over several days is meaningful.

The German-language S2k guideline describes the evaluation rule of the Sensiplan method for this, called “3 over 6” for short (AWMF 015-095). In four steps:

1. Find the first value that is higher than the six values directly before it.
2. Mark the highest of those six lower values and draw a horizontal reference line at its level.
3. Check whether the next two values are also above the reference line, so that you have three higher values in a row.
4. The third higher value must be at least 0.4°F (0.2°C) above the reference line.

If all conditions are met, the temperature rise counts as having occurred. For borderline cases, the guideline names two exceptions:

• Third value too close to the line: If the third higher value is less than 0.4°F (0.2°C) above the reference line, you wait for a fourth value. If it is also above the reference line, the rise counts as confirmed, and a gap of 0.4°F (0.2°C) is then not needed.
• One outlier downward: If a single value between the higher values falls on or below the reference line, you do not count it. The third higher value must then be at least 0.4°F (0.2°C) above the line, though (AWMF 015-095).

According to the S2k guideline, you can use the method for reliable contraception only if you have learned it well, for example in qualified natural family planning (NFP) counseling (AWMF 015-095).

The WHO family planning handbook puts the rule more simply: If the temperature stays above its usual level for 3 full days, the fertile phase is considered over (WHO 2022). That is not definitive proof of ovulation (NICE NG257).

Do not rely on a dip shortly before the rise. According to FSRH, this often-described dip is missing in many cycles. In a study of 101 women, the dip was a poor predictor of ovulation (Guermandi 2001).

Example chart: one cycle as a table

Here is how the rule looks in a made-up example. The numbers are not normal values. How high your temperature sits in absolute terms does not matter for the evaluation; what counts is the rise compared with your own earlier values.

What the table shows:

• The rise is confirmed on day 16. Ovulation was probably shortly before the first higher value, because temperature usually rises 1 to 2 days after ovulation, sometimes on the day itself (familienplanung.de). So here it was roughly between day 12 and 14.
• The most fertile days are over by the time the rule applies. According to ACOG, they are the 2 to 3 days before the rise, here roughly day 11 to 13.
• The high phase lasts 13 days, then the temperature drops and your period comes. For comparison: The second half of the cycle (luteal phase) lasts 14 days on average, and 11 to 17 days is normal (ASRM 2026).

Basal body temperature chart template: a table to fill in

Whether paper, spreadsheet, or app: With these columns you can evaluate your values later and explain outliers. Write the measuring site once at the top of the sheet; it stays the same.

Keep filling in row by row until your next period starts. You need the columns for cervical mucus and LH test if you combine the methods; you can read more in the section Combining basal body temperature with cervical mucus and ovulation tests.

Basal body temperature after ovulation: the rise and the high phase

How much the temperature rises is stated differently by different sources: 0.4 to 0.9°F (0.2 to 0.5°C) according to the WHO, about 0.4°F (0.2°C) according to familienplanung.de. So we are talking about only a few tenths of a degree, which is why you need a thermometer with two decimal places (IQWiG 2025).

According to a study by the university women’s hospital in Dresden, the size of the rise is not suitable for diagnosing a luteal phase defect. The reason: Temperature responds to the amount of hormone only within a low progesterone range (Goeckenjan 2020, sensors supplied by the manufacturer).

The elevated temperature lasts until menstruation (FSRH 2015). Without fertilization, it drops again shortly before or during the next period (familienplanung.de). The length of the high phase thus gives you an impression of the second half of your cycle, which lasts 14 days on average, with 11 to 17 days being normal (ASRM 2026).

Pregnant? What a long high phase of your basal body temperature can mean

If you are pregnant, your temperature does not drop before the expected period; it stays elevated. If it is still elevated 18 days after fertilization, according to the Federal Institute for Public Health, that is almost always a sure sign of pregnancy (familienplanung.de).

However, you do not know the exact day of fertilization. As a guide: A high phase that lasts clearly longer than the usual 11 to 17 days of the second half of a cycle (ASRM 2026) can be an indication. A pregnancy test gives certainty.

A prolonged high phase can also have other causes. Fever or an infection also raise the morning temperature (IQWiG 2025), and with fever the method is hard to use according to the WHO (WHO 2022).

Short or missing high phase: an indication, not a diagnosis

Sometimes the chart does not rise at all or only briefly. What that can mean:

• No high phase (monophasic chart): Cycles without ovulation usually show a monophasic chart. Some women who do ovulate, however, do not have a clearly biphasic chart (ASRM 2021).
• Short high phase: According to the S2k guideline, cycle charting can give indications of a luteal phase defect (high phase shorter than 10 days) or of absent ovulation (AWMF 015-095). ASRM sets the limit slightly differently and speaks of a luteal phase defect when the second half of the cycle is 10 days or less; other definitions name 9 or 11 days (ASRM 2026). A greatly shortened high phase of under 10 days can, according to ASRM, also point to a milder ovulation disorder (ASRM 2021). That is not a diagnosis: According to ASRM, no test for luteal phase defect has proven reliable (ASRM 2026).

For perspective: Short second halves of the cycle are also common in women who ovulate. In a study of 259 women with regular cycles, the luteal phase was shorter than 10 days in 8.9% of cycles with ovulation (Schliep 2014). According to ASRM, a shortened luteal phase was not associated with lower fertility over 12 months (ASRM 2026).

So look at your chart over several cycles and discuss anything unusual with your gynecologist. What can be behind a short second half of the cycle and what is documented about progesterone, you can read in the guide Luteal phase defect.

Disruptors: what distorts your basal body temperature

An elevated morning temperature does not have to come from ovulation (IQWiG 2025). These factors are named as sources of disruption:

We did not find numbers for how many degrees most of these factors shift the values. Mark such days in your table so that you do not mistake a single outlier for the start of the high phase.

If you work shifts or constantly sleep at different times, the chart is hard to read (Henry 2024). It is then worth looking at other signs such as cervical mucus or LH tests.

How reliable is basal body temperature? The limits of the method

Reading the day of ovulation from a chart is harder than it looks. Studies that compared the chart with hormone measurements or ultrasound show this:

The guidelines assess the chart differently:

• NICE (UK, 2026): Basal body temperature charts should not be used to confirm ovulation because they do not reliably predict it (NICE NG257, recommendation 1.18.9).
• ESHRE (Europe, 2023): In women with regular cycles, tests to confirm ovulation are not routinely recommended. If confirmation is indicated, urinary LH measurement, ultrasound, or progesterone in the middle of the second half of the cycle can be used. Basal body temperature is described as less accurate and less accepted by patients.
• ASRM (USA, 2021): Because of the effort and the lack of accuracy, measuring is not routinely recommended today, especially if the cycle history suggests ovulation.
• ACOG (USA, 2025): On its own, basal body temperature is neither well suited for preventing pregnancy nor for getting pregnant, because it only shows that ovulation has already happened.
• Germany, Austria, and Switzerland (S2k guidelines): The guideline on fertility diagnostics names ovulation tests and cycle self-monitoring as options to supplement or replace medical cycle monitoring or laboratory diagnostics in the second half of the cycle (AWMF 015-085, 2026). The guideline on contraception sees cycle charting as a diagnostic tool that can give indications of a cycle without ovulation or of a short high phase (AWMF 015-095). The German-language guidelines are thus more restrained in their criticism than NICE and ESHRE.

Does measuring basal body temperature help when you want to get pregnant?

Whether timed intercourse after cycle observation with methods such as basal body temperature, cervical mucus, or a calendar changes the number of live births is uncertain according to the 2023 Cochrane review. Compared with intercourse without ovulation prediction, the relative risk was 0.95 (95% CI 0.76 to 1.20; 2 studies with 157 participants; low-quality evidence).

For urine ovulation tests, things look better: According to Cochrane, intercourse after ovulation testing probably increases the live birth rate (relative risk 1.36; 95% CI 1.02 to 1.81; 1 study with 844 women; moderate-quality evidence). Where 16 of 100 women had a baby without prediction, it would be 16 to 28 of 100 with the test.

A caveat: What was tested was not a simple test strip but a commercial fertility monitor that measures LH and an estrogen breakdown product (E3G). The couples were fertile and had been trying to get pregnant for no more than 6 months. The evidence was downgraded, among other things, because of commercial funding (Cochrane 2023).

On the symptothermal method, which combines temperature and cervical mucus, there is an observational study of 187 women who had been trying to get pregnant for 3.5 years on average: After training in the Sensiplan method, 38% were pregnant after 8 months. Without training, the authors estimated 21.6%, derived from only 7 pregnancies before the training. There was no control group. Several of the authors belong to the Natural Fertility section of the German Society for Gynecological Endocrinology and Reproductive Medicine, which developed Sensiplan (Frank-Herrmann 2017).

More important than any chart is regular sex. According to ASRM, cycle observation should only supplement timing and not replace frequent intercourse every 1 to 2 days in the fertile window; strict timing can also cause stress. The chance per cycle was similar with sex daily, every other day, and every 3 days in the fertile window (ASRM 2022). NICE names sex every 2 to 3 days (NICE NG257). So the chart is a tool for getting to know your cycle, not a schedule for the bedroom.

Combining basal body temperature with cervical mucus and ovulation tests

Each sign looks at a different moment in the cycle. Together they complement each other: mucus and LH test for the days before ovulation, temperature as a look back afterward.

Cervical mucus: According to ASRM, it is a useful supplementary sign. In a study of 2,832 cycles, the changes in the mucus ran closely parallel to basal body temperature and predicted the most fertile time more accurately than a cycle calendar. In a large study, the mucus pattern predicted the probability of conception per day at least as well as basal body temperature or an LH urine test (ASRM 2022). Temperature and mucus together make up the symptothermal method.

LH test: An ovulation test announces ovulation; temperature rises only afterward. In an analysis by an app manufacturer, the first positive LH test and the ovulation day estimated from temperature were on average 1.9 days apart (Berglund Scherwitzl 2015). You can read how to use LH tests correctly in the guide Ovulation test, and what the hormone value does in your cycle in the article LH levels.

Calendar: Pure calendar apps hit the actual day of ovulation in at most 21% of cases in a study of 949 women. The first authors are employed by a manufacturer of ovulation tests (Johnson 2018). Our Ovulation Calculator also calculates by calendar. It is a planning aid for getting started, not a confirmation of ovulation.

Basal thermometer: criteria instead of a test winner

You do not need a device with an app. According to IQWiG, a digital thermometer that measures to two decimal places is the most suitable. Here is what you can look for when buying:

Some apps also accept readings from other basal thermometers with two decimal places that you enter by hand. In our research, Bluetooth basal thermometers with an app cost €49.90 to €149, with the more expensive bundles including a permanently unlocked app. For some models, an app subscription of €39.99 to €83.92 a year is added, and with one provider the thermometer is only available together with the annual subscription for €119.99 (as of October 2026).

You will not find a basal thermometer review with a test winner here. Independent measurements of the accuracy of individual models were not available to us; the accuracy figures come from the manufacturers.

For apps and fertility trackers that rely mainly on basal body temperature, according to the S2k guideline, effectiveness studies are missing, or the existing ones have considerable methodological weaknesses. The guideline refers to contraception here and currently does not recommend such systems for reliable contraception (AWMF 015-095). What wristbands, rings, and vaginal sensors achieve according to studies is covered in the next section.

Wearables: wristband, ring, and sensor

Instead of measuring in the morning, you can also have your temperature recorded overnight. Wristbands and finger rings measure the temperature of the skin. According to the S2k guideline, this peripheral temperature does not correspond to basal body temperature, and such systems are considered experimental for contraception there (AWMF 015-095). There are also sensors that measure core body temperature vaginally overnight.

What studies show:

• 2026 meta-analysis: Wearables identified the fertile window correctly somewhat more often than self-measured basal body temperature, with a pooled accuracy of 88% (95% CI 86% to 90%) versus 75% (63% to 86%). Wearables hit the exact day of ovulation with a pooled accuracy of 56%, but the confidence interval ranges from 0% to 100%, so the estimate is practically not informative. Within ± 1 day, accuracy was 61%, within ± 2 days 90%, and within ± 3 days 88%. In irregular cycles the devices performed worse, and the quality of the evidence was very low (Shi 2026).
• Wristband versus basal body temperature: In a study with 57 healthy women and 193 cycles, compared with a home LH test, skin temperature at the wrist detected more ovulations than orally measured basal body temperature (sensitivity 62% versus 23%). But it also reported ovulation more often in cycles without ovulation (specificity 26% versus 70%), although there were only 23 such cycles. One author was employed by the wristband manufacturer, another had been employed there earlier, and a further author sat on its advisory board (Zhu 2021).
• Disruptors apply at night too: In a study with 194 participants that was co-funded by the manufacturer, sex and a large meal in the 3 hours before sleep were also associated with nighttime skin temperature, as were 5 or more units of alcohol. The cycle-related rise remained detectable anyway (Shilaih 2018).
• With cycle disorders: The authors of a study on a finger ring, all employed by the manufacturer, advise interpreting ovulation estimates with caution in cycle disorders such as polycystic ovary syndrome (PCOS) (Thigpen 2025). What the next steps can look like with PCOS is covered in the guide Getting pregnant with PCOS.

You can find the measuring principle, costs, and evidence for individual devices, from the thermometer app to the hormone monitor, in the fertility tracker comparison.

When to discuss your chart with a doctor

First something reassuring: Anyone with a regular monthly cycle very likely ovulates (NICE NG257, recommendation 1.18.6). More than 80% of heterosexual couples get pregnant within a year if the woman is under 40 and the couple has regular sex without contraception (NICE NG257).

Talk to your gynecologist if your chart stays monophasic over several cycles, the high phase is repeatedly very short, or your cycle is irregular. If getting pregnant does not work, the German-language guideline recommends an evaluation after 12 months, after 6 months for women over 35, and immediately at a fertility clinic for women over 40 (AWMF 015-085, 2026). According to NICE, if a cause is suspected or from age 36, a referral for specialist fertility advice should be offered already at the first doctor’s appointment (NICE NG257).

Whether ovulation takes place can be checked more accurately with progesterone in the blood in the middle of the second half of the cycle, in a 28-day cycle around day 21 (NICE NG257, recommendation 1.18.7). A value above 3 ng/ml indicates recent ovulation according to ASRM (ASRM 2026). NICE recommends the measurement in the fertility workup even with a regular cycle, while ESHRE does not recommend it routinely with a regular cycle. The guidelines do not agree on this.

Only your doctor can put your chart in context, so bring your records to the appointment. Which tests exist is covered in the guide Fertility test for women, and the infertility guide describes the path of evaluation for both partners.

Frequently asked questions

When is the best time to take your basal body temperature?

Right after waking up, before you get up. IQWiG advises a fixed time of day (IQWiG 2025), while the S2k guideline no longer considers this necessary (AWMF 015-095). The required rest beforehand is also stated differently: 1 hour according to frauenaerzte-im-netz.de, at least 3 hours according to FSRH.

How much does basal body temperature rise after ovulation?

By a few tenths of a degree, roughly 0.4 to 0.9°F (0.2 to 0.5°C) depending on the source (WHO 2022, frauenaerzte-im-netz.de). It usually rises 1 to 2 days after ovulation, sometimes on the day itself (familienplanung.de). For the evaluation, what counts is the rise compared with your own values, not a particular target value.

Can I measure basal body temperature in the mouth or under the armpit?

In the mouth yes, under the armpit no. The S2k guideline names oral, vaginal, and rectal (AWMF 015-095), IQWiG vaginal and rectal (IQWiG 2025). Orally measured values are on average about 0.4°F (0.2°C) lower than rectally measured ones, so always measure at the same site. The armpit is too inaccurate (frauenaerzte-im-netz.de).

How can I tell from my basal body temperature that I am pregnant?

In a pregnancy, the temperature stays elevated instead of dropping before your period. If it is still elevated 18 days after fertilization, according to familienplanung.de that is almost always a sure sign of pregnancy. Fever also raises the values, and a pregnancy test gives certainty.

Can I predict ovulation with basal body temperature?

No. The temperature rises only after ovulation. In a small study, the rise came on average 2.4 to 4.1 days after the LH peak in the blood, depending on the evaluation method (Prior 1990). LH tests or observing your cervical mucus show you the days before (ASRM 2022).

What does a chart without a rise mean?

A monophasic chart can point to a cycle without ovulation. Some women who do ovulate, however, do not have a clearly biphasic chart (ASRM 2021). If your chart stays flat over several cycles, have it checked by a gynecologist, for example with a progesterone value in the second half of the cycle (NICE NG257).

Do I need a basal thermometer with an app?

No. According to IQWiG, a digital thermometer with two decimal places is suitable, and you can write down the values on paper or in an app (IQWiG 2025). For apps and fertility trackers that rely mainly on temperature, according to the S2k guideline, effectiveness studies on contraception are missing, or they have considerable methodological weaknesses (AWMF 015-095).

What basal body temperature is normal?

You do not need a fixed normal value for the evaluation. What counts is the rise compared with your own earlier values: after ovulation by a few tenths of a degree, roughly 0.4 to 0.9°F (0.2 to 0.5°C) depending on the source (WHO 2022, frauenaerzte-im-netz.de). Where you measure shifts the values: Measured orally, they are on average about 0.4°F (0.2°C) lower than measured rectally (frauenaerzte-im-netz.de).

Sources

Guidelines and position statements

• Family Planning: A Global Handbook for Providers, chapter Fertility Awareness Methods, WHO and Johns Hopkins Bloomberg School of Public Health (CCP), 2022
• FSRH Clinical Guidance: Fertility Awareness Methods, Faculty of Sexual & Reproductive Healthcare (now CoSRH), 2015
• Diagnostics and therapy before medically assisted reproduction treatment, S2k guideline AWMF 015-085, version 2.0, DGGG, OEGGG, and SGGG, as of April 2026
• S2k guideline Non-hormonal contraception, AWMF 015-095, version 1.1, DGGG, OEGGG, and SGGG, as of December 2023
• NICE NG257: Fertility problems, assessment and treatment, Investigation of fertility problems and management strategies, NICE, March 31, 2026
• NICE NG257: Initial advice to people concerned about delays in conception, NICE, March 31, 2026
• NICE NG257: Defining infertility and initial assessment, NICE, March 31, 2026
• Evidence-based Guideline: Unexplained Infertility, ESHRE, 2023
• Fertility evaluation of infertile women: a committee opinion, Fertil Steril 2021;116:1255-65, ASRM Practice Committee, 2021
• Optimizing natural fertility: a committee opinion, Fertil Steril 2022;117:53-63, ASRM Practice Committee, 2022
• Diagnosis and treatment of luteal phase deficiency: a committee opinion, Fertil Steril, ASRM Practice Committee, 2026
• Fertility Awareness-Based Methods of Family Planning (FAQ024), ACOG, last reviewed February 2025

Health information

• Contraception with natural family planning methods, gesundheitsinformation.de, IQWiG, 2025
• Determining your fertile days yourself: methods, frauenaerzte-im-netz.de (BVF and DGGG), last edited July 9, 2018
• How do I measure my body temperature?, frauenaerzte-im-netz.de (BVF and DGGG), last edited July 10, 2018
• Getting pregnant: ovulation and the fertile days, familienplanung.de (Federal Institute for Public Health), January 7, 2026
• Am I pregnant?, familienplanung.de (Federal Institute for Public Health), September 8, 2020
• Basal Body Temperature: Family Planning Method, Cleveland Clinic, 2022

Studies

• Bauman JE: Basal body temperature: unreliable method of ovulation detection, Fertil Steril 1981;36(6):729-33
• Prior JC, Vigna YM, Schulzer M, Hall JE, Bonen A: Determination of luteal phase length by quantitative basal temperature methods: validation against the midcycle LH peak, Clin Invest Med 1990;13(3):123-31
• Guermandi E et al.: Reliability of ovulation tests in infertile women, Obstet Gynecol 2001;97(1):92-6
• Schliep KC et al.: Luteal phase deficiency in regularly menstruating women: prevalence and overlap in identification based on clinical and biochemical diagnostic criteria, J Clin Endocrinol Metab 2014;99(6):E1007-14
• Henry S, Shirin S, Goshtasebi A, Prior JC: Prospective 1-year assessment of within-woman variability of follicular and luteal phase lengths in healthy women, Hum Reprod 2024;39(11):2565-2574
• Gibbons T et al.: Timed intercourse for couples trying to conceive, Cochrane Database Syst Rev 2023, CD011345.pub3
• Frank-Herrmann P et al.: Natural conception rates in subfertile couples following fertility awareness training, Arch Gynecol Obstet 2017;295(4):1015-1024
• Goeckenjan M et al.: Continuous Body Temperature Monitoring to Improve the Diagnosis of Female Infertility, Geburtshilfe Frauenheilkd 2020;80(7):702-712
• Berglund Scherwitzl E, Lindén Hirschberg A, Scherwitzl R: Identification and prediction of the fertile window using NaturalCycles, Eur J Contracept Reprod Health Care 2015, written by the manufacturer
• Johnson S, Marriott L, Zinaman M: Can apps and calendar methods predict ovulation with accuracy?, Curr Med Res Opin 2018

Wearables and apps

• Shi Y et al.: The diagnostic accuracy of wearable digital technology in detecting fertility window and menstrual cycles: a systematic review and Bayesian network meta-analysis, npj Digital Medicine 2026;9:139
• Zhu TY et al.: The Accuracy of Wrist Skin Temperature in Detecting Ovulation Compared to Basal Body Temperature, 2021, authors with ties to the manufacturer
• Shilaih M et al.: Modern fertility awareness methods: wrist wearables capture the changes in temperature associated with the menstrual cycle, Biosci Rep 2018;38(6):BSR20171279, co-funded by the manufacturer
• Thigpen N, Patel S, Zhang X: Oura Ring as a Tool for Ovulation Detection: Validation Analysis, J Med Internet Res 2025, authors employed by the manufacturer
• Alfawzan N, Christen M, Spitale G, Biller-Andorno N: Privacy, Data Sharing, and Data Security Policies of Women's mHealth Apps, JMIR mHealth uHealth 2022

Law

• Regulation (EU) 2017/745 on medical devices (MDR), Article 2, point 1, European Parliament and Council, 2017
• Regulation (EU) 2016/679 (GDPR), Article 9, European Parliament and Council, 2016