The Creighton Model FertilityCare System is not the rhythm method. The calendar rhythm method is based on statistical guesswork to identify the day of ovulation. The CrMS is based on a reliable sign of your fertility, and works no matter how long, short, regular, or irregular your cycles may be.

The CrMS is not natural birth control. It does not suppress or alter your natural fertility in any way. But it can be used as a natural means for true family planning- meaning that it can be used reliably either to avoid pregnancy or to conceive.