Diaphragms, sponges and cervical caps are evolving. Future versions of diaphragms and cervical caps should be easier to insert and remove, yet harder to dislodge during sexual intercourse. They will be made of silicone rubber, which has a longer shelf life than does latex rubber and is safe for users with latex allergy. Sponge development, in general, aims at reducing vaginal irritation by lowering spermicide doses.
Diaphragms
Studies involving some 2,800 U.S. women suggest that, during typical use, the diaphragm may be somewhat more effective than the contraceptive sponge or cervical cap.1 However, disadvantages of conventional diaphragms are that they must be fitted by a provider, are made of latex rubber, can be unwieldy to insert and remove, and should not be left in place for longer than 24 hours.
Two diaphragm-like devices have been designed to resolve some of these problems: the Lea's Contraceptive and the SILCS intravaginal barrier (pronounced "silks"). Both come in one size; thus, clients need not be fitted for the devices. Both are made of silicone rubber, not latex.
The Lea's Contraceptive, a cup-shaped barrier with a loop for removal, can be left in place for up to 48 hours. It also features a one-way valve to allow for the passage of cervical secretions and assure a tight fit. It is available over-the-counter in Germany, but has not been approved by the U.S. Food and Drug Administration (FDA). A study conducted by the U.S.-based Contraceptive Research and Development (CONRAD) Program and FHI indicated that pregnancy rates compared favorably with those reported in other studies of barrier contraceptive methods, including the cervical cap, sponge and diaphragm.2 CONRAD research found 12-month pregnancy rates associated with the use of Lea's Contraceptive to be 15 percent, compared with 10 percent to 21 percent for the use of a diaphragm with spermicide.3
However, because of the relatively small number of women in that study, the FDA is requiring larger clinical trials of the device, one of which CONRAD is conducting. FDA approval is needed before a contraceptive can be included in U.S. foreign aid programs.
The SILCS intravaginal barrier -- developed by the U.S.-based Program for Appropriate Technology in Health (PATH) and a private company called SILCS, Inc. -- is being compared with the standard latex diaphragm in a CONRAD clinical trial. The SILCS barrier has a shape and dimpled surface intended to make insertion and removal easier. Its cost is expected to be relatively low, and its manufacturer has an agreement to develop it for use in developing countries.
Research about the potential of diaphragm devices to reduce STD transmission is limited. Whether it protects against HIV is unknown. However, a diaphragm may provide some protection by covering the cervix, which may be the principal site of HIV transmission.4
Sponges
Currently, two contraceptive sponges -- called Protectaid and Pharmatex -- are available, primarily in Canada and Europe. A third, the Today sponge, was introduced to the U.S. market in 1983, was removed in 1995, but is expected to return. Clinical trials of the contraceptive efficacy of a fourth sponge, called Avert, are planned and may begin soon.
All four sponges are manufactured in one size, allowing women to buy them over-the-counter without the help of a provider. All four have the common contraceptive qualities of blocking the cervix, trapping sperm and releasing spermicides. All sponges are designed to be effective for many hours -- some as long as 24 hours -- regardless of the number of acts of sexual intercourse during this period. Being able to insert them hours in advance is considered an important feature to many women who use them. However, the sponges must be left in place at least six hours after last intercourse, and women should avoid leaving them in beyond the maximum recommended time.
The Pharmatex sponge, marketed in Europe, contains 60 mg of the spermicide benzalkonium chloride (BZK). The Today sponge, containing 1,000 mg of the spermicide nonoxynol-9 (N-9), was a popular device on the U.S. market until its owner discontinued making it for financial reasons unrelated to the product itself. However, concentrations of spermicides found in these two sponges -- while capable of killing pathogens that cause many sexually transmitted diseases -- can irritate the vaginal lining. Theoretically, women exposed frequently and for long periods of time to such spermicide concentrations may develop vaginal abrasions that could facilitate HIV transmission. Thus, researchers are studying sponges with less spermicide.
The Protectaid sponge, marketed in Canada since 1996 and recently approved for marketing in Europe, contains three spermicides (N-9, BZK, and sodium cholate) in relatively small concentrations. The Avert sponge is expected to have 100 mg of N-9. The Protectaid and Avert sponges have the advantage of being wet -- water is not needed before they are used.
Clinical studies to determine the effect of contraceptive- sponge use on STD infection are limited. Only the results of studies of the Today sponge are available.
An FHI study in Thailand of 225 women at high-risk for STDs indicated that women using the N-9-containing Today sponge were less likely to have contracted chlamydial infection and gonorrhea than women not using the sponge.5 Another study, conducted among 138 sex workers in Nairobi, Kenya, found that the risk of contracting gonorrhea was reduced by 60 percent among women using the sponge containing N-9, compared with placebo users.6 However, significantly more women using the N-9 sponge developed genital ulcers (an important risk factor for HIV infection), and 45 percent of 60 women in the N-9 group, versus 36 percent of 56 women in the placebo group, became infected with HIV. Notably, women in the study used the N-9 sponge repeatedly each day for long periods. "It is possible that less frequent use might be associated with a lower risk of adverse effects or even with protection against HIV infection," the authors concluded.
Estimated 12-month pregnancy rates for the typical use of the N-9-impregnated Today sponge are 17 percent (14 percent for nulliparous women and 27 percent for parous women).7 Reported 12-month pregnancy rates for women -- regardless of parity -- using the Protectaid sponge are 23 percent for typical use.8
Cervical caps
Conventional caps can be worn up to 48 hours. However, they are made of latex, must be fitted by a provider, and can be difficult to insert or remove.
Two new cervical caps are under development. The first, called FemCap, is made of silicone and can be worn up to 48 hours. Shaped like a hat with an upturned brim (that lies against the vaginal walls around the cervix), it is easier to insert than conventional caps. It places no pressure on the urethra, unlike conventional diaphragms. This may explain why it has been associated with significantly fewer urinary tract infections than the conventional diaphragm, although these fewer infections may be due to the fact that FemCap uses less spermicide than the diaphragm. A strap recently has been added to the FemCap to facilitate removal, and the redesigned device is being tested by CONRAD, with FHI collaboration.
In a CONRAD and FHI study, FemCap used with spermicide was found to be somewhat less effective as a contraceptive than a conventional diaphragm with spermicide.9 FemCap also appears to be less effective than a conventional cap. CONRAD research indicates a 12-month pregnancy rate, based on reported six-month pregnancy rates, of about 23 percent for FemCap. The estimated 12-month pregnancy rate for the conventional cap is 18 percent (ranging from 15 percent for nulliparous women to 30 percent for parous women).10
The second new cervical cap, the Oves Cap, is a silicone device that can be left in place for three consecutive days. Equipped with a removal loop, it is disposable after one use. Although sold in France, it is not FDA-approved. CONRAD is conducting a clinical trial to study this cap's acceptability, ease of placement, and how likely it is to dislodge during sexual intercourse.
All cervical caps have the disadvantage of requiring a fitting because they come in at least two sizes. Research is needed to determine whether cervical caps provide any protection against STDs, although it is theorized that HIV entry via the cervix may be impeded by cap use.
-- Kim Best
References
Development and testing of vaginal contraceptives: addendum to final report. Unpublished paper, Family Health International, 1985; Trussell J, Sturgen K, Strickler J, et al. Comparative contraceptive efficacy of the female condom and other barrier methods. Fam Plann Perspect 1994;26(2):66-72; Bernstein GS. Use-effectiveness study of cervical caps. Unpublished paper. Los Angeles Regional Family Planning Council, 1986.
Mauck C, Glover LH, Miller E, et al. Lea's Shield: a study of the safety and efficacy of a new vaginal barrier contraceptive used with and without spermicide. Contraception 1996;53(6):329-35.
3. Hatcher RA, Trussell J, Stewart F, et al., eds. Contraceptive Technology, Seventeenth Revised Edition. (New York: Ardent Media, Inc., 1998)818-21.
Haase A. The pathogenesis of sexual mucosal transmission: obstacles to and opportunities for prevention. Microbicides 2000 Conference. Alexandria, VA, March 13-16, 2000; Anderson D. Genital tract inflammation, microbicides, and HIV transmission. Microbicides 2000 Conference. Alexandria, VA, March 13-16, 2000.
Rosenberg MJ, Feldblum PJ, Rojanapithayakorn W, et al. The contraceptive sponge's protection against Chlamydia trachomatis and Neisseria gonorrhoeae. Sex Transm Dis 1987;14(3):147-52.
Kreiss J, Ngugi E, Holmes K, et al. Efficacy of nonoxynol 9 contraceptive sponge use in preventing heterosexual acquisition of HIV in Nairobi prostitutes. JAMA 1992;268(4):477-82.
Family Health International; Trussell.
Colin P, Creatsas G, Serfaty D, et al. Multinational, open phase II study of the efficacy, safety and acceptability of the Protectaid contraceptive sponge. Annual meeting of the Society of Gynecologists and Obstetricians of Canada, Ottawa, Canada, June 1999.
Mauck C, Callahan M, Weiner DH, et al. A comparative study of the safety and efficacy of FemCap, a new vaginal barrier contraceptive, and the Ortho All-Flex diaphragm. The FemCap Investigator's Group. Contraception 1999;60(2):71-80.
Bernstein; Trussell.
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