Sponge versus diaphragm for contraception: a Cochrane review

Abstract

The contraceptive vaginal sponge was developed as an alternative to the contraceptive diaphragm. Unlike the diaphragm, the sponge can be used for more than one coital act within 24 h without the insertion of additional spermicide, and it does not require fitting or a prescription from a physician. We conducted a systematic review of randomized controlled trials that compared the vaginal contraceptive sponge with the diaphragm used with a spermicide in order to evaluate the efficacy and continuation rates of the two devices. The sponge was statistically significantly less effective in preventing overall pregnancy than was the diaphragm in the two trials that met our inclusion criteria. The 12-month cumulative life table termination rates per 100 women for overall pregnancy were 17.4 for the sponge versus 12.8 for the diaphragm in the larger US trial, and 24.5 for the sponge and 10.9 for the diaphragm in the UK trial. Similarly, discontinuation rates at 12 months were higher with the sponge than with the diaphragm [odds ratio 1.3; 95% confidence interval (CI) 1.1–1.6]. Allergic-type reactions were more common with the sponge in both trials, although the frequency of discontinuation for discomfort differed in the two trials. Other randomized controlled trials will be needed to resolve the role of spermicides in preventing sexually transmitted infections or in causing adverse effects.

Introduction

Although vaginal contraceptives have been used for millennia, little is known about their contraceptive efficacy [1]. Contemporary methods include spermicide, the female condom, the cervical cap, the diaphragm and the contraceptive vaginal sponge. The Today sponge (VLI Corporation, Irvine, CA, USA) is a single-use, soft polyurethane device approximately 2.5 cm thick with a diameter of 5.5 cm and an indentation on one side to facilitate its placement against the cervix. The sponge is designed to prevent pregnancy primarily through the gradual release of the spermicide nonoxynol-9 and, to a lesser extent, by blocking the cervix and absorbing semen.

Advantages of the vaginal sponge and the diaphragm include a lack of hormonal side effects and medical contraindications; control of the method by the woman rather than by her partner; and the ability to insert the device in advance of intercourse and to leave it in place for repeated acts of intercourse. Both devices can be used for more than one coital act within 24 h, but, unlike the diaphragm, the sponge does not require the insertion of additional spermicide for repeat coitus. The sponge also has the advantage over the diaphragm of not requiring a prescription or fitting from a health care provider. Although the cost of the diaphragm and its fitting make the device more expensive than the sponge initially, the diaphragm can be used for years. The sponge is relatively inexpensive, but the recurrent cost of the disposable method could be prohibitive for some. The sponge and diaphragm must be used correctly and consistently with each act of intercourse in order to be effective in preventing pregnancy. Also, some women consider the two contraceptive methods intrusive. Limited evidence [2] suggests that the sponge, as well as the diaphragm [3], could increase the risk of toxic shock syndrome. Furthermore, high concentrations of nonoxynol-9 in the vagina from sponge or diaphragm use could potentially cause adverse effects [4].

Participants in the two large trials of the sponge were instructed to leave the device in place for no more than 48 h. However, when the US Food and Drug Administration approved the device for use in the US, they used a more conservative limit of 24 h due to a lack of data from both trials relating to the duration of sponge use. The recommended 24-h limit is not based on data showing an increase in pregnancy or complications related to longer use, but is due to a lack of evidence.

The Today sponge has been approved for sale in numerous nations including Singapore (1981); the United Kingdom, the Netherlands and Norway (1982); and the United States and Switzerland (1983). The sole US manufacturer ceased production of the Today sponge in 1995 after the US Food and Drug Administration imposed new manufacturing standards. However, the Today sponge was purchased by Allendale Pharmaceuticals in 1998 and the sale of the product in the US is expected to resume.