# Pre-ovulatory phase

The pre-ovulatory phase indicates the first phase of a menstrual cycle and starts with your first day of menstrual bleeding. It marks the phase that takes place "prior to ovulation". During this phase you can assume that you are infertile for a determined amount of days until fertility must be assumed. There is a set of rules that needs to be applied in order to know exactly for how many days this phase lasts.

## 5 day rule

If during your last cycle you have detected a valid temperature shift not before cycle day 12, you can assume infertility for the first 5 days in the following new cycle. If the secondary symptom (cervical mucus or cervix) indicates fertility, e.g. egg white cervical mucus on cycle day 4, you have to assume that you are fertile and the pre-ovulatory phase will end immediately.

## Minus 8 rule

In addition if you have at least tracked valid temperature shifts for your last 12 menstrual cycles, you can apply the minus 8 rule: Out of the last 12 cycles, take the earliest temperature shift and subtract 8 days from it to determine the length of your pre-ovulatory phase.

##### Example a:

The earliest temperature shift out of your last 12 cycles happened on cycle day 11.

- 11 days - 8 = 4 days of assumed infertility.

##### Example b:

The earliest temperature shift out of your last 12 cycles happened on cycle day 15.

- 15 days - 8 = 7 days of assumed infertility.

If you have tracked ovulation for more than just your last 12 cycles, then the earliest ever recorded ovulation determines the length of your pre-ovulatory phase forever.

## Minus 20 rule

If you have at least tracked the length of your last 12 menstrual cycles, you can apply the minus 20 rule: Out of the last 12 cycles, take the shortest one and subtract 20 days from it to determine the length of your pre-ovulatory phase. This rule is not yet being applied in drip.

##### Example a:

The shortest cycle out of your last 12 cycles lasted 24 days.

- 24 days - 20 = 4 days of assumed infertility.

If you have tracked more than just your last 12 cycles, then the shortest ever recorded cycle determines the length of your pre-ovulatory phase.

If you find fertile mucus or cervix at the beginning of your cycle, you have to immediately assume fertility and the beginning of a peri-ovulatory phase.