Effectiveness depends on the user: Risk of pregnancy is greatest when couples have sex on the fertile days Effectiveness Arrowwithout using another method.

  • As commonly used, in the first year about 15 pregnancies per 100 women using periodic abstinence.This means that 85 of every 100 women relying on periodic abstinence will not become pregnant. Most of the couples in this study were using the calendar rhythm method.
  • Pregnancy rates with consistent and correct use vary for different types of fertility awareness methods (see table, below). These rates reflect the experience of couples who volunteered to use these methods in research projects (see Question 3). Reliable effectiveness rates are not available for the calendar rhythm method or the basal body temperature method.
  • In general, abstaining during fertile times is more effective than using another method during fertile times.

Pregnancy Rates With Consistent and Correct Use and Abstinence on Fertile Days

Pregnancies per 100 Women Over the First Year
Method Consistent and correct use As commonly used
Standard Days Method 5 12
Two Day Method 4 14
Ovulation method 3 23
Symptothermal method <1 2

These rates reflect the experience of couples who volunteered to use these methods in research projects. Reliable effectiveness rates are not available for calendar rhythm or the basal body temperature method.

Return of fertility after fertility awareness methods are stopped: No delay

Protection against sexually transmitted infections (STIs): None