Q: I was recently married and have been using a diaphragm for birth control. I would like to know how the effectiveness of this method compares with other methods.
A: A study of various contraceptive measures during the first year of marriage showed that the failure rate (percentage of women who became pregnant during one year despite the use of a contraceptive) was lowest for oral contraceptives and highest for the rhythm method. Failures also were frequent with the use of a diaphragm. It is not clear that the pregnancy rate is decreased by using a spermicide in combination with a diaphragm.
In this study the failure rates for methods of contraception were as follows: oral contraceptives, 2.5; intrauterine device, 4.8; condom, 9.6; diaphragm, 14.4; spermicide, 17.7; and rhythm, 18.8. With the exception of the condom, the same relative effectiveness was observed for these contraceptive methods in a study done in the early '80s in married women who were over 30 and had an annual income greater than $15,000. In these women the failure rate for the other methods were one-half to one-third of those above.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine and associate dean for faculty affairs at the school.
