+49 2131 460 410

Calculating fertile days

There are several methods for calculating a woman's fertile days. Here are the most important facts, rules and methods:

Only six days in a woman's cycle are fertile: the five days before ovulation and the day of ovulation. Ovulation occurs 10-16 days before the next menstruation. Irregular cycle lengths of 23-35 days are normal, and so ovulation and fertile days can only be determined through observation. There are several methods for this:

1. Cervical mucus: On days of high fertility, the cervical mucus is stretchy, like raw egg white. This provides a hospitable environment for sperm and fertilisation cannot take place without it.

2. Temperature: On fertile days, body temperature is usually 2/10 lower than on the days following ovulation. Analysing the temperature curve produces an conclusive picture of whether ovulation has actually occurred, when the fertile period has definitely come to an end and whether the menstrual cycle is disturbed.

3. Hormones: A rise in the level of the sexual hormones LH and E3G shows the fertile days prior to ovulation. These hormones can be measured at home using test sticks or by a doctor using a blood test.

4. Ultrasound: Shows the current development of the follicles in the ovaries.

What is analysed?MethodAdvantagesDisadvantages
Cervical mucusSensiplan, Rötzer, Billingscan be used anywhere, provides best indication of days of high fertility, excellent basis for further medical treatmentMeasuring process has to be learned, daily observation recommended
TemperatureContraception monitors, temperature method, Sensiplan, RötzerCan be used at home, provides indication of fertile days, end of fertile period, disturbances to the cycle, pregnancy. Excellent basis for further medical treatmentDaily measurement recommended, manual analysis of data has to be learned (except for contraception monitors)
Hormones levels in urineFertility monitors, ovulation testsClearly indicate fertile daysSeveral tests needed at the right time
Hormone levels in bloodOnly at the doctor'sSnapshot of current stage of the menstrual cycleHas to be carried out by a doctor on the right days of the cycle
UltrasoundOnly at the doctor'sClearest indication of the exact day of ovulationHas to be carried out by a doctor on the right days of the cycle

Recommended reading: "Was ist los in meinem Körper?" Dr. med. Raith-Paula, Pattloch Verlag - a book for girls and young women - described the complex processes involved in the female menstrual cycle in a way that is both readable and easy to understand.