A Cochrane review included 2 RCTs comparing cervical cap and the diaphragm (both vaginal barrier contraceptive methods covering the cervix and acting as a reservoir for spermicide). The Prentif cap was comparable to the diaphragm in preventing pregnancy (OR 1.24, 95% CI 0.89–1.74, n=1153), but the FemCap was not as effective as its comparison diaphragm (OR 1.77, 95% CI 1.02–3.07, n=748). The Prentif cap had a higher proportion of Class I–III cervical cytologic conversions at the three-month visit than the diaphragm (OR 2.3, 95% CI 1.0–5.1), while there were no differences in Papanicolaou smear results between the FemCap and the diaphragm. Prentif cap users had fewer vaginal ulcerations or lacerations (OR 0.3, 95% CI 0.1–0.7) than diaphragm users. FemCap users had more often blood in the device on removal (OR 2.3, 95% CI 1.3–4.1), but fewer urinary tract infections (OR 0.6, 95% CI 0.4–1.0) than those in the diaphragm group.
Comment: The quality of evidence is downgraded by limitations in study quality and by imprecise results (limited study size for each comparison).