Contraceptive efficacy of the diaphragm, the sponge and the cervical cap

A reanalysis of data from two clinical studies--in which 1,439 women were randomly assigned to use either the contraceptive sponge or the diaphragm and 1,394 women were randomly assigned to use either the cervical cap or the diaphragm--found first-year probabilities of failure during typical use of 17% for the sponge, 18% for the cervical cap and 13-17% for the diaphragm. The first-year probabilities of failure during perfect use are 11-12% for the sponge, 10-13% for the cervical cap and 4-8% for the diaphragm. The probability of failure during perfect use is significantly higher among women who have given birth than among those who have not for users of the sponge (19-21% vs. 9-10%) and users of the cervical cap (26-27% vs. 8-10%), but not for users of the diaphragm.