During Apple's WWDC 2019 Event, Apple's VP of Health, Dr. Sumbul Desai introduced the 'Cycle Tracking' app for Apple Watch that tracks a woman's menstrual cycle. It's also available in the iPhone's Health app. Below is the video of Dr. Desai introducing this new app.

Today the US Patent & Trademark Office published a patent application from Apple titled "In-Bed Temperature Array for Menstrual Cycle Tracking." Apple appears to have invented a new Menstrual Cycle Tracking System for their Beddit Sleep Monitoring System company.

In Apple's patent background they note that a menstrual cycle starts with the first day of a period and ends when the next period begins. The first part of the cycle--pre-ovulation--prepares an egg to be released from an ovary and builds the lining of the uterus. Then, at ovulation, an egg is released from the ovary. The second part of the cycle prepares the uterus to accept a fertilized egg or to start a new cycle if pregnancy doesn't occur.

A woman may be most likely to get pregnant during the two to three days before ovulation, and may desire to track their menstrual cycle for a variety of reasons including natural family planning.

An entire menstrual cycle typically lasts between 24 and 38 days, but the length may vary from cycle to cycle, and may also change over time (e.g., with age or changes in health). A woman may track her menstrual cycle using the basal body temperature (BBT) method, which typically includes the user measuring and recording her temperature every morning. An increase in temperature usually indicates that ovulation has occurred.

Because the most fertile window occurs prior to ovulation, a user will typically track her menstrual cycle for multiple months to predict when she is likely to ovulate. The ovulation day may also be used predict the start date of the next menstrual cycle. However, variation in lengths of the cycle and subtle increases in temperature can make it difficult for some users to reliably predict the ovulation day.

Apple's invention covers a method for tracking a menstrual cycle of a user. The method can include receiving temperature measurements from one or more temperature sensors in an array of temperature sensors positioned under the user on a bed an determining a use period for the array of temperature sensors when temperature measurements from at least one temperature sensor of the one or more temperature sensors exceeds a first temperature threshold for a duration.

The method can also include identifying a set of temperatures that are within the use period and exceed a second temperature threshold, and, for each use period in a set of two or more use periods, determining a temperature of the user using the set of temperatures from the respective use period. The method can further include identifying at least one change in the temperature of the user between different use periods after determining the temperature of the user for each use period in the set of two or more use periods, and estimating an ovulation day of the user based on the at least one change in the temperature of the user.

Apple's patent FIG. 1 below illustrates an example temperature sensing system for menstrual cycle tracking design as a bed accessory. FIG. 3 shows an example output from a temperature sensing device that is used for menstrual cycle tracking; and FIG. 4 shows an example analysis that may be performed by a temperature sensing system for menstrual cycle tracking.

Apple's patent FIG. 5 below shows an example method of operating a temperature sensing system for menstrual cycle tracking.

For more details, review Apple's patent application number 20220047250.  Considering that this is a patent application, the timing of such a product to market is unknown at this time.