Comparison of Birth Control Methods - Effectiveness Calculation

Effectiveness Calculation

Failure rates may be calculated by either the Pearl Index or a life table method. A "perfect-use" rate is where any rules of the method are rigorously followed, and (if applicable) the method is used at every act of intercourse.

Actual failure rates are higher than perfect-use rates for a variety of reasons:

• mistakes on the part of those providing instructions on how to use the method
• mistakes on the part of the method's users
• conscious user non-compliance with method.
• insurance providers sometimes impede access to medications (e.g. require prescription refills on a monthly basis)

For instance, someone using oral forms of hormonal birth control might be given incorrect information by a health care provider as to the frequency of intake, or for some reason not take the pill one or several days, or not go to the pharmacy on time to renew the prescription, or the pharmacy might be unwilling to provide enough pills to cover an extended absence.