Thermometer for precise measurement of miniscule changes in a woman’s temperature.
Temperatures of 36.9°C plus or minus six-tenths of a degree are registered. Label: Taking the temperature before getting out of bed is recommended. Do not use in the event of a fever above 38°C.
The box is labelled Zyklotest D.R.P.
The temperature is taken daily to determine the onset of ovulation, which is accompanied by an increase in the body’s temperature amounting to a few tenths of a degree. Knowledge of this increase can be useful for family planning, either contraception or determining fertility.
Checking the temperature is less than practical for purposes of contraception, as it requires a regular menstrual cycle, a uniform daily routine and an iron will to remain abstinent on days when sex could result in pregnancy.
The temperature must be taken at the same time every day before breakfast, between 6 and 8 a.m., after at least six hours of uninterrupted sleep. The same thermometer must be used according to the same method (oral or rectal). Stress, colds and travel can influence the result.
After: Holt, J. G. H., Geburtenregelung auf biologischem Wege - Der Zusammenhang zwischen Fruchtbarkeit und Körpertemperatur der Frau (‘Natural Birth Control - The Relationship between Fertility and a Woman’s Body Temperature’), 1959