Variable Cycle Length and the Billings Method

The introduction to Cycle Variations illustrated that the length of the pre-ovulatory phase may vary considerably, and that the time from ovulation to the beginning of menstruation in a fertile woman is between 11 and 16 days, or about 2 weeks.

The graphical record is a bar chart.

The height of each bar shows the level of fertility:

There are six examples included below. Each example* depicts a set of ovulation cycles sequencing from shorter to longer cycles, and within a set there are similarities in the build up to ovulation.

The one woman may experience all these example cycles during her fertile life.

Type of Example	Basic Infertile Pattern
	Dry	Unchanging Discharge
Continuous BIP until change before ovulation	Example 1	Example 2
BIP interrupted by more than one change	Example 3	Example 4
BIP interrupted by changes and bleeding	Example 5	Example 6

* The concept for the graphics on these pages originated in a teaching aid called the "slide rule" that was designed by Bernadette de Bruyn of Melbourne.