Fertility charting and fertility awareness methods rely on the tracking of basal body temperature to help confirm ovulation in retrospect. Most fertility awareness methods rely on the data collected using basal body temperature readings. This is an indication of core temperature at rest. BBT thermometers can be used orally, vaginally and rectally. While BBT thermometers remain the most accurate way to monitor temperature for fertility, the practice of taking temperature each morning is not suitable for everyone. With the rise in technology, more companies are innovating ways to make temperature monitoring for fertility more convenient for women. There are various types of thermometers and wearable temperature taking devices that are available in the market, each with their unique features and capabilities.
It is important to note that the majority of the new temperature devices are not based on internal basal body temperature but rather measure external proximal or distal skin temperatures. Proximal skin temperature thermometers measure the temperature of the skin on the arm, thigh or wrist, and they are designed to provide an alternative to BBT thermometers. They are easy to use and do not require insertion into the body. Distal skin temperature thermometers measure the temperature of the skin on the fingers or toes. They are designed to provide an alternative to BBT thermometers and are often used in conjunction with other fertility tracking methods. Proximal and distal skin temperatures are NOT reflective of basal body temperature, however are still responsive to the menstrual cycle hormones and so can therefore still be used to track fertility. The accuracy in which they do this is dependant on the device and also on how well the person responds to the device. There is very limited evidence on this new form of temperature monitoring for fertility and so much of the evidence we have is based on women trialling and comparing different devices and comparing them to traditional BBT measurements.
In this article, I am providing a rundown of some of the most popular thermometer choices for fertility awareness and am grouping them into those which are compatible with fertility awareness method and those which are not. It is not a comprehensive list and only mentions the most popular devices available at the time of writing this post. No matter which device a woman chooses to use, it is important to avoid any integrated apps that claim to be able to predict ovulation based on temperature trends. Temperature has no predictive ability and is only used as a marker to confirm ovulation in retrospect. Using calculations and algorithms based on temperature trends (such as the cycles app) might be convenient, but its not true fertility awareness method. Attempting to predict ovulation based on temperature trends puts women at risk of unintended pregnancy or can make the trying to conceive journey unnecessarily long. In all cases, the device used to take temperature should simply be used as raw data to input into a chart that can then be assessed by the woman (or fertility instructor) and not as a means to predict the fertile window and ovulation.
Compatible with Fertility Awareness Methods
Basal body thermometers (BBT) are widely used for fertility charting and are available in different forms such as oral, vaginal, and rectal thermometers. BBT thermometers are designed to measure the temperature with high accuracy (2 decimal places) and precision, and they are the most common type of thermometer used for fertility tracking. The most common way to use these thermometers is orally. These thermometers are inexpensive and easily accessible at many pharmacies as “ovulation thermometers” or Basal Body Thermometers. My favourite thermometer and the one I use personally is is this Surgipack thermometer from chemist warehouse (valued at $13 AUD) but there are many other alternatives online and in different pharmacies.
Tempdrop: Tempdrop is a wearable device that measures the temperature of the skin on the upper arm. It is designed to provide a more accurate and convenient way of measuring basal body temperature. The device is worn throughout the night, and the data is synced with a mobile app for analysis. Tempdrop is well accepted device in fertility awareness and is most commonly recommended for women with erratic sleep schedules such as women in post-partum or women who have shift work. The price is around $300 AUD
BBRing: BB Ring from FemTek is a wearable device that measures the temperature of the skin on the finger as well as heart rate and heart rate variability. This device is created specifically for fertility charting and is still in development and available for pre-order (but with promising effectiveness). The BBRing is similar to the Tempdrop in that it learns to cut out disturbances during sleep and can therefore provide an average basal body temperature reading. It is a good option for those with erratic sleep schedules. The device is worn throughout the night, and the data can be synced with a mobile app. It does not offer ovulation predictability however offers suggested insights into adapting lifestyle based on the different phases of the menstrual cycle and even has “breastfeeding trackers”. The device aims to increase body awareness and is a good option for those interested in cycle syncing. The price is around $400 AUD including the additional charger.
Not Compatible with Fertility Awareness Methods:
Daisy Thermometer is a basal body thermometer that can measure temperature accurately within 1/100th of a degree. The device connects to a mobile app, allowing users to track their fertility and ovulation periods. Although the Daisy thermometer is very accurate, it uses algorithms to predict the fertile window and ovulation based on temperature calculations. Any device that uses calculations to predict the fertile window is not compatible with Fertility Awareness Methods.
Ava Bracelet: Ava Bracelet is a wearable device that measures various physiological parameters, including skin temperature, heart rate, and respiratory rate. It is designed to provide a comprehensive view of the body’s physiological responses and is particularly useful for fertility tracking. The device is targeted specifically for women trying to conceive and works by predicting the 5 most fertile days in the fertile window based on the data collected by the bracelet. The device is only suitable for those with regular cycles between 26-35 days and attempting pregnancy. It is not compatible with fertility awareness methods.
Oura Ring, Apple Watch and Fitbit: These are devices not specifically designed for fertility but ones that measure sleep and fitness. These devices do not measure temperature but rather require a temperature baseline to provide accurate temperature measurements. A temperature baseline is the average temperature of an individual’s body at a specific time of day. Users of these devices need to establish a baseline by consistently measuring their temperature at the same time each morning for several days. Once a baseline is established, the device can compare subsequent temperature readings to the established baseline. These recordings focuses more on identifying trends away from baseline eg. your temperature was 0.4 degrees higher than baseline. It is important to note that changes in factors such as physical activity, stress, and illness can affect the accuracy of the temperature readings, even when a baseline has been established. The baseline itself is not constant and may need to be updated. In order to use these temperature readings accurately the woman must add or subtract the changes to her baseline each day and record it into a charting app (extra maths). According to users, the Fitbit is also highly inaccurate. These devices are not compatible with fertility awareness methods but are worth mentioning as technology is likely to evolve and may potentially improve.