With proper training and use, the Billings Ovulation Method® has been verified as 99% effective for avoiding pregnancy. It's effectiveness is comparable to the most effective forms of hormonal contraception, but without any of the risks or side effects. The Billings Ovulation Method® also has higher effectiveness than IUDs and barrier contraceptives.
The method-related pregnancy rate is achieved when couples follow all the instructions for the method of birth control.
The use-related pregnancy rate includes couples who did not follow or misunderstood the instructions of the method of birth control.
Billings rates taken from the China trial, a 12 month multi-center trial which included 992 couples. This trial occurred from 1996-1997.
Figures for the Pill and contraceptive devices taken from Family Planning: A Global Handbook for Providers.
For a look at earlier trials on the effectiveness of the Billings Ovulation Method® only: Trials of the Billings Ovulation Method