Editorial Feature

Fertility Monitoring Sensors

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Many couples who are trying to conceive turn to fertility monitors. The use of a female fertility monitoring sensor is becoming increasingly popular among couples in modern-day society.

A fertility monitoring sensor is designed to estimate fertile and infertile periods in a woman’s menstrual cycle. The process is based on detecting changes in the concentration of the female hormone human chorionic gonadotropin (hCG) and luteinizing hormone (LH) in the urine. The hCG hormone is released by a fertilized ovum, and the presence of this hormone in urine is a classic marker for indicating pregnancy.

Being able to conceive is not as easy as may be assumed, especially if one or both partners have infertility. According to NHS statistics, approximately one in seven couples find it difficult, or near impossible, to have a baby; nearly 3.5 million people living in the UK.

Out of the percentage of couples trying to conceive, 80 percent can achieve this within one year of having unprotected sex and with no medical intervention. To diagnose the cause of infertility, couples are encouraged to use several fertility tests.

Comparing Persona and DuoFertility Monitoring Sensors

Following the success of the ClearBlue home pregnancy test kit, a new era of home testing kits started to help increase the accuracy of fertility monitoring; the use of which is now becoming an initial step in family planning for couples struggling to conceive.

Unipath, Unilever’s leading pregnancy test business, has provided some famously-known home fertility testing kits, including Persona – introduced in 1996 and used to monitor hormone levels in urine so that the female will know when she is most fertile and able to conceive.

The Persona

The Persona device is a handheld sensor and disposable test stick based on an optical reading mechanism to indicate fertility status. The test kit uses a urine sample to convert essential reproductive hormones, displaying the detection of these hormones as a colored signal, and the monitor interprets this color variation.

Such a test must be taken on specific days so that the monitor can gather information on the concentration of a pregnancy hormone over a certain period to indicate fertility.

The test stick converts the level of estrone-3-glucuronide (E-3-G, a secretory form of the hormone estradiol and is used as an ovarian indicator function) and LH into a color that can be interpreted by the monitor.

There is an algorithm used by the monitor to convert the E-3-G and LH concentrations. The test stick is made of a wicking material containing a latex reagent. The reagent is created from blue particles that have antibodies specific to the E-3-G hormone, allowing them to immobilize the hormone onto the wick.

The stick is also made up of a membrane onto which the E-3-G protein will conjugate. During a standard test whereby urine is introduced to the test stick, the urine moves along the wick through capillary action. This runs the latex to the test patch where it has contact with E-3-G. Hence, a decrease in the latex color indicates high levels of E-3-G in the sample.

The latex in the test stick is also made of antibodies that will attract the â-subunit of LH, indicating the presence of this hormone in a sample of urine. As this is an assay technology, measurements on the concentration of a sex hormone are based on optical transmission data. When using the primary monitor, a light beam is projected through the membrane of the test stick, and several photodetectors detect the transmitted light through this membrane.

An increase in the number of color changes causes a decrease in the intensity of light emitted through the membrane. A reduction in the color status of the E-3-G test patch due to a high concentration of this hormone leads the monitor to change the fertility from safe (green light) to unsafe (red light).

The monitor can archive test data for a period of up to 6 months, and this information will be based on changes in hormone levels, menstrual cycle, and the status of fertility possible, through an algorithm that is coded with a series of microprocessors.


Measuring the level of sex hormones in urine is the most accurate parameter for a home fertility testing kit. However, DuoFertility is an example of a home testing kit that is designed to measure basal temperature as an indicator of fertility. This test kit will indicate when a female is likely to conceive, up to six days prior. The DuoFertility device is designed with a sensor connected to a reader.

The sensor is attached to an adhesive patch that is worn by the female and is sensitive to skin temperature (with this sensor being able to record 20,000 temperature measurements during a period of sleep), providing accurate readings of temperature associated with the state of ovulation.

The DuoFertility reader is wirelessly connected to the sensor patch and displays the status of fertility on a screen. The video below discusses the main functional steps to the DuoFertility sensor kit.

Sensor technology is making a mark in the medical industry for its use in family planning. With so many couples using fertility testing electronic devices, it is becoming an initial step in indicating which day could heighten the chances of conception.

The fact that, like Persona, these devices can store data on fertility patterns, makes them an essential piece of equipment for physicians. The stored data can help understand why couples are having problems conceiving and can often support the diagnosis and treatment of infertility.

Fertility Monitoring Apps

Today, alongside fertility sensors, there are also fertility monitoring apps. The development of smartphones allowed women to track fertile and infertile periods effectively.

Over the years, several mobile phone fertility apps have emerged. These apps contain many features, such as a menstrual calculator, ovulation calculator, basal body temperature chart, fertility treatments, cervical data, and connections to a thermometer and other health apps.

References and Further Reading

  • Wild, D. (2005). The Immunoassay Handbook. UK, Oxford: Elsevier Ltd.
  • NHS Statistics/Infertility.
  • Swiss Precision Diagnostics GmbH.  
  • May, K. Home Monitoring with the ClearPlan EasyTM Fertility Monitor for Fertility Awareness. The Journal of International Medical Research. 2001; 29(Suppl 1): 14A–20A.
  • DuoFertility. Advanced Fertility Monitor.

This article was updated on the 18th July, 2019.

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