femSense – combining the Temperature Method with OPKs for a more accurate fertile window.

Young woman looking at your smartphone. on the right side the cycle calendar with the ovulation is marked.

While using OPKs with femSense isn’t required, combining the two methods of ovulation can be really helpful in identifying the most fertile days in the month. When you combine femSense with OPKs, you’re keeping an eye on two different signals from your body that help detect ovulation. You can add LH test results to the femSense app so that you can see in your personal history when your LH levels surge before ovulation and we can use this data to make our algorithm even more precise.

As part of our continued development of the femSense app and preparation for femSense Birth Control we are gathering information about the LH surge and how it relates to each individual women and her ovulation. Adding this additional information to our algorithm will allow us to predict a woman’s fertile window with greater accuracy and add to the reliability of the femSense system.

Ovulation is a process not an instantaneous event.

Ovulation is a complex process which lasts up to 24hours, but the body is preparing to ovulate for even longer. In your ovaries tiny eggs are developing in sacs called follicles, these are the eggs released at ovulation. Your body knows that it is time to release an egg when oestrogen levels reach their peak during your menstrual cycle. The brain produces a surge of Luteinizing Hormone (LH) which triggers ovulation. This LH surge typically occurs 24 – 40 hours before ovulation and traces of the hormone can be detected in urine. This is what LH ovulation tests are looking for. After ovulation your progesterone levels rise which causes your body temperature to rise too. It is this tiny rise in temperature that femSense can detect. The rise in temperature is a direct result of ovulation and that is why only the temperature method can confirm ovulation. Once you have ovulated you are fertile for approximately 24 hours.

Steps in ovulation

  • Oestrogen levels peak causing a surge in LH
  • Ovulation begins and a follicle releases a mature egg
  • After ovulation the empty follicle turns into the corpus luteum
  • Corpus luteum causes Progesterone levels to rise
  • Higher progesterone causes body temperature to rise

While ovulation test strips measure the presence of LH (Luteinizing Hormone) in the urine as an indication that the body is preparing to ovulate, femSense uses the temperature method to measure and confirm that ovulation has taken place. In other words, LH tests are measuring the beginning of the fertile window and the temperature method is measuring the end.

How does adding LH test results (OPK’s) to the femSense app help me identify my fertile window?

LH tests, which are also known as OPK‘s (Ovulation Prediction Kits) are commonly used to predict ovulation. OPK’s show that LH levels are rising and that the body is preparing to ovulate. LH ovulation test strips measure the LH concentration in the urine which increases as the body prepares for ovulation. Most OPK strips look and work just like home pregnancy tests, you pee on a test strip and wait for the lines to appear. A positive result means that your LH levels are rising, and you can expect to ovulate soon. A surge in LH indicates that the body is preparing to ovulate and that you are entering your fertile window. A positive LH test is therefore a good indication of the beginning of the fertile period.

femSense uses the temperature method to measure and confirm that ovulation has taken place. At ovulation a woman’s basal body temperature rises by a tiny amount and remains slightly higher for the second half of her cycle. This minute rise in body temperature is therefore a direct result of ovulation and is a reliable indication that ovulation has occurred. If ovulation had not taken place there would be no rise in temperature. This means, the temperature method detects ovulation after it has happened. In fact the temperature method is the only “home test” that can confirm ovulation.

In short: LH tests measure a rise in hormone levels BEFORE ovulation while femSense uses the temperature method to detect the rise in temperature that happens AFTER ovulation.

This is why these two different methods of ovulation detection often show results on different days during your fertile window. OPK’s and femSense are measuring different bodily signals which occur at different times in the process of ovulation. Used together however they can accurately measure the beginning and end of your fertile window - the days shortly before and just after ovulation.

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How can adding LH test results to my femSense app can help the accuracy of the femSense algorithm?

We are continuously updating and improving the femSense app and of course the algorithm behind it which predicts the fertile window. Although an independent Swiss statistics institute recently confirmed that femSense is 99.73% accurate when predicting the fertile window, we still see room for improvement, particularly when femSense is used as a method of birth control. That is why it is now not only possible to add LH test results to the app, but we encourage it! In this way our algorithm can “learn” more about the menstrual cycle and make even more accurate predictions. A woman’s cycle is more than just her period, it is a fluctuation of hormones which influence her both mentally and physically.

The more we learn about women’s menstrual cycles, the better we can understand and support their reproductive health. And you can help! Anonymously and privately.

How does adding my LH results to the femSense app help other women?

Thanks to technology and research, we now know more about the complicated hormonal changes that happen during a woman’s menstrual cycle This has helped create innovative new products like the femSense sensor patch, ovulation predictor kits (OPKs), and apps to track fertility. These tools help women understand their menstrual cycle and figure out when they are most likely to get pregnant. By offering these services, we can empower women to take control of their reproductive health and make smart choices about family planning. However, there is still more to learn!

The amount of research done on women’s health and menstrual cycles has been hugely inadequate. However, we now have a chance to gather information and improve our understanding of these topics. By using femSense patches and tracking LH readings, we can gain insights into the fertile window and ovulation process, information which can be used to educate women about their fertility and improve their reproductive health. You too can be part of this revolution, anonymously and privately. Simply add your LH measurements to the femSense app while you are wearing the sensor patch. This will help us to narrow down your fertile window but also learn more about the process of ovulation. From the LH surge signaling that the body is preparing to ovulate until the rise in basal body temperature which confirms that ovulation has taken place.

Together we are stronger! Thanks for your support!