The field of electronics plays a vital role in designing clinical equipment ranging from a small digital thermometer to complex health monitoring systems. Even critical implantable devices (such as cochlear implants, cardiac pacemakers) rely on electronics for signal conditioning. This series of articles will discuss the electronic design of certain widely used medical devices. This first installment focuses on the design of a fertility monitor.
Need for a fertility monitor
A fertility monitor is a small portable device used to monitor the fertility levels of a woman by checking the hormone levels in her body. Because a woman doesn’t have the same level of fertility every day, when a woman wants to get pregnant, she tends to look for a day when the fertility level in her body is at the highest. A fertility monitor test hormone levels to identify when levels are the highest.
Typically, a woman’s menstrual cycle has a duration of 28 days. This overall menstrual cycle has three phases where the peak fertility occurs during a period between the second and the third phases. This period of peak fertility is also known as the ovulation period. Certain hormonal changes during the ovulation period can result in measurable changes like an increase in luteinizing hormone (LH) in urine and an increase in basal body temperature (BBT) (usually one or two days before ovulation).
The following images (see Figure 1 and Figure 2) show how the LH- hormone concentration and the basal body temperature (BBT) are distributed throughout the 28-day cycle period.
Figure 1: LH concentration vs. days
Click on image to enlarge
Figure 2: BBT vs. days