Editorial Feature

Fertility Monitoring Sensors

The use of a female fertility monitor is becoming increasingly popular among couples in modern-day society striving to conceive. This electronic device is designed to estimate the fertile and infertile periods in a woman’s menstrual cycle – a process that is based on detecting change in the concentration of the female hormone human chorionic gonadotropin (hCG) and luteinizing hormone (LH) in urine. The hCG hormone is released by a fertilised 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 one may assume, especially if one or both partners are suffering from infertility. According to statistics by the NHS, approximately one in six to seven couples find it difficult or near to impossible to have a baby, a fraction that reflects approximately 3.5 million people living in the UK. Out of the percentage of couples trying to conceive, 80 per cent are able to achieve this within the one year of having unprotected sex and no medical intervention. In order to diagnose the cause of infertility, couples are encouraged to use a number of fertility tests. The range of fertility tests currently on the market are summarised in the list below:

  • Luteinizing hormone monitors (Clearblue Easy, Persona)
  • Thermal Monitors (DuoFertility, Lady-Comp, Baby-Comp, Pearly)
  • Electrolyte monitors (OvaCue and OvWatch)
  • Cyclothermal monitor (Cyclotest)

Considering the range of over-the-counter fertility test kits available, attention will be given to the  comparison of Persona and DuoFertility test kits as both measure fertility status by using different parameters (i.e., sex hormones and basal temperature, respectively). Following the success of the ClearBlue home pregnancy test kit, a new era of home testing kits had started to advance to help increase the accuracy of monitoring fertility, use of which is now becoming an initial step in family planning for those couples struggling to conceive. Unipath, Unilever’s leading pregnancy test business, has given birth to 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 the fertility status. The test kit uses a urine sample to convert key reproductive hormones and displays the detection of these hormones as a coloured signal and this colour variation is interpreted by the monitor. Such a test has to be taken on a certain number of days so that the monitor can gather the information on the concentration of a pregnancy hormone over a certain period of time to indicate fertility.

The test stick to Persona converts the level of estrone-3-glucuornide (E-3-G, a secretory form of the sex hormone estradiol and is used as an indicator ovarian function) and LH visually into a colour 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 that contains a latex reagent made of blue particles that have antibodies specific to the E-3-G hormone allowing them to immobilize this 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, through capillary action the urine moves along the wick which the moves the latex to the test patch where it then has contact with E-3-G, hence a decrease in the latex colour 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 to indicate the presence of this hormone in a sample of urine. As this is assay technology, measurements on the concentration of a sex hormone is based on optical transmission data. When using the main monitor, a light beam is projected through the membrane of the test stick and the transmitted light through this membrane is detected by a number of photodetectors (sensors). An increase in the amount of colour change results in a decrease in the intensity of light emitted through the membrane. So, a decrease in the colour status of the E-3-G test patch, due to a high concentration of this hormone, causes the monitor to change the fertility from safe (green light) to unsafe (red light). The monitor can archive test data for up to a period of 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.

DuoFertility

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 status as opposed to measuring the concentration of a sex hormone in a sample of urine. 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 measurements of temperature 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 clearly making a mark in the medical industry for its use in family planning. With so many couples using fertility testing electronic devices, it is clearly becoming a good initial step in indicating on which day sexual intercourse is advisable to heighten the chances of conception. The fact that, like Persona, these devices can store data on fertility patterns, this then becomes a key piece of equipment for physicians to help understand the stored data in order to help couples having problems conceiving and can often support the diagnosis and treatment of the infertility.

Reference

  • 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.

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