The cervical cap and the diaphragm are small, rubber devices that women put in their vagina (birth canal) and place over their cervix. Both devices block sperm and help prevent pregnancy. Also, both hold a chemical that kills sperm. Birth control with these methods can be stopped at any time and can be used without involving the partner. The cervical cap is smaller than the diaphragm and can be left in place longer. The cervical cap can be worn up to 72 hours, and the diaphragm can be used up to 30 hours. In this review, we compared the cervical cap with the diaphragm for how well it worked for birth control. We also looked at its safety and whether women stopped using it early.
We did a computer search for studies of cervical caps. We wrote to manufacturers and researchers for information about other trials. We included randomized controlled trials that compared a cervical cap with a diaphragm.
We found two trials that compared the cervical cap with the diaphragm. Two types of cervical caps were studied: the Prentif cap and the FemCap. The Prentif cap prevented pregnancy as well as the diaphragm, but the FemCap did not. Women who used the Prentif cap had more abnormal changes in the cervix than diaphragm users. The FemCap users did not have more abnormal changes than the diaphragm users. Many women from both groups dropped out early from the two trials. Similar numbers of FemCap users and diaphragm users reported liking their assigned method.
The Prentif cap worked as well as the diaphragm to prevent pregnancy. The FemCap did not prevent pregnancy as well as the diaphragm. Both cervical caps appear to be medically safe.