Background
Contemporary rankings and ratings of contraceptive options frequently neglect the Billings’ ovulation method or cite inaccurate failure rates for this method.

Aims
The aim of the review is to clarify inaccurate data and to shed light on the role Billings’ discoveries play in contemporary research on contraception.

Methods
Systematic analysis of the failure rates of the most widely used ratings and rankings offered by influential research institutes and government agencies.

Results
Contemporary research uses Billings’ insights for stipulating new characterizations of contraceptive methods and fails to agree on estimates for these methods.

Conclusion
New data are needed to accurately assess the efficacy of the Billings’ ovulation method and to determine its place in international rankings.