Because the research design for the clinical trial establishing the contraceptive efficacy of the female condom--a six-month life-table probability of failure of 15% (12% in the United States vs. 22% in Latin America)--did not include randomization with another method of contraception, no definite conclusion about its comparative efficacy is possible. Comparisons using other female barrier methods as historical controls, however, provide evidence that, among women in the United States, the contraceptive efficacy of the female condom during typical use is not significantly different from that of the diaphragm, the sponge or the cervical cap. The six-month probability of failure during perfect use of the female condom is 2.6% among U.S. women, similar to rates for the diaphragm and the cervical cap but significantly lower than that for the sponge. Meaningful comparisons with the male condom are not possible because of the lack of data from carefully controlled prospective clinical trials. Extrapolations from the results on contraceptive efficacy suggest that perfect use of the female condom may reduce the annual risk of acquiring the human immunodeficiency virus by more than 90% among women who have intercourse twice weekly with an infected male.
PIP: The research design for clinical trials of the female condom did not include randomization with another contraceptive method, so no one can definitely determine its contraceptive efficacy. Less formal comparisons with studies of other barrier methods reveal that the contraceptive efficacy of the female condom during typical use is not different from that of other vaginal barrier methods among US women. When researchers standardize probabilities of failure by parity and age, the diaphragm may be more effective than the female condom, the sponge, and the cervical cap during typical use. Yet, during perfect use, the contraceptive efficacy of the female condom is the same as that of the diaphragm, at least that of the cervical cap, and greater than that of the vaginal sponge. The clinical trial of the female condom did not include women with low coital frequency, included chemically confirmed pregnancies even when they were not clinically confirmed, and lost a much smaller percentage of the sample to follow-up than other clinical trials. Thus, one would expect the female condom to have higher failure rates than the other barrier methods, even if the contraceptive efficacies of the barrier methods matched. It is impossible to conduct statistical comparisons of the contraceptive efficacies of the female condom and the male condom because no carefully controlled clinical trials of the male condom have been conducted. The contraceptive efficacy of the female condom is probably similar to that of the male condom without a spermicidal lubricant, even though a superficial comparison with published probabilities of failure suggests otherwise. Extrapolations from results on contraceptive efficacy suggest that the female condom has the potential of reducing the annual risk of HIV infection by more than 90% among women having intercourse two times a week with an HIV-infected male.