Contraceptive computers are minicomputers the size of a spectacle case or a cigarette box. They are designed to make identification of the fertile days of the cycle more reliable and more convenient.

All devices are based on a similar principle. The data of the individual menstrual cycle are stored electronically and used to calculate the fertile and infertile days.

Temperature computers

Temperature computers record the basal body temperature and analyze the measurements. A light signal or tone indicates the fertile and infertile days. The products of different manufacturers differ mainly in technical details such as the size of the memory and the display.

Hormone tests

'Hormone computers' detect the hormone levels in the first morning urine using test strips. They measure the female sex hormone estrogen and the pituitary hormone LH which triggers ovulation at midcycle. The two hormones are eliminated in high concentrations on the fertile days.

The hormone computer analyses the result of the urine test and uses colored lights to indicate whether there is a risk of conception or not.

The hormone computer can only be used by women with a cycle length between 23 and 35 days. There are some women for whom the computer is not suitable.

According to the manufacturers the hormone computers have an effectiveness of 94 percent.