Diaphragm (contraceptive) - Effectiveness

Effectiveness

The effectiveness of diaphragms, as of most forms of contraception, can be assessed two ways: method effectiveness and actual effectiveness. The method effectiveness is the proportion of couples correctly and consistently using the method who do not become pregnant. Actual effectiveness is the proportion of couples who intended that method as their sole form of birth control and do not become pregnant; it includes couples who sometimes use the method incorrectly, or sometimes not at all. Rates are generally presented for the first year of use. Most commonly the Pearl Index is used to calculate effectiveness rates, but some studies use decrement tables.

For all forms of contraception, actual effectiveness is lower than method effectiveness, due to several factors:

• 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

For instance, someone using a diaphragm might be fitted incorrectly by a health care provider, or by mistake remove the diaphragm too soon after intercourse, or simply choose to have intercourse without placing the diaphragm.

Contraceptive Technology reports that the method failure rate of the diaphragm with spermicide is 6% per year.

The actual pregnancy rates among diaphragm users vary depending on the population being studied, with yearly rates of 10% to 39% being reported.

Unlike some other cervical barriers, the effectiveness of the diaphragm is the same for women who have given birth as for those who have not.