BARRIER CONTRACEPTIVE METHODS
Barrier methods were the only reversible methods of contraception generally available until the introduction of oral contraceptives and the newer generation of plastic and copper intrauterine devices in the 1960’s and 1970’s. Since then their use has diminished considerably but in certain countries they have recently enjoyed a renewal of interest.
Barrier methods to prevent the upward passage of spermatozoa in the female genital tract have been advocated for thousands of years. Initially, sponges impregnated with lemon juice were suggested and even vaginal pessaries of crocodile manure were used in Egypt more than three thousand years ago.
In 1564, the condom was described as a method for the prevention of sexually transmitted disease and cloth condoms or those made from animal intestines were used for this purpose until the discovery of vulcanization of rubber and the development of latex condoms in the 19th century. By the 18th century, the contraceptive usefulness of the condom was being recognized and it is estimated that in the 1980’s up to 8% of married women used the condom. In 1986, the United States’ authorities called for condom use for the prevention of human immunodeficiency virus transmission and condom sales rose sharply—between 20 and 50% annually. In developing countries, the use of condoms for contraception varies from country to country. In Hong Kong in 1988, up to 26% of married couples used condoms but only 1-9% in Central and South America and 1-7% in Asia and the Pacific countries.
The diaphragm and cervical caps form a physical barrier to the passage of sperm by being placed over the cervix thus occluding the cervical canal. These methods alone are not reliable and are usually used in conjunction with a spermicide. The latex rubber diaphragm was invented in 1882 under the name of Mensinga and has undergone only minor changes since. The differences between diaphragms are in the type of metal spring in the perimeter of the device and the number of different sizes that are available. The use of diaphragms in developing countries is not popular because of the high failure rate, the lack of privacy for insertion and removal of the device, the need for the device to be fitted at the first visit, lack of clean water for washing the device, and the need for spermicides to be used with the device. Probably less than 5% of contraceptive users in developing countries choose the diaphragm or cervical caps.
The cervical cap, which is designed to fit closely over the cervix, is being actively promoted as an alternative method of contraception. However, the device has many of the disadvantages of the diaphragm and, in addition, it requires more accurate placement over the cervix and thus more genital manipulation and a greater understanding of the subject’s own anatomy.
A very large range of substances have been used over the centuries as a vaginal method of contraception. Though the modern spermicides are not strictly barrier methods, they are usually used together with diaphragms and cervical caps. In developing countries, few married couples of reproductive age rely only upon spermicides for contraception. Modern-day spermicides come as foaming tablets, pessaries, creams, films, impregnated sponges, and spray foams. Studies from the USA and the United Kingdom have shown unacceptably high pregnancy rates amongst women using spermicides as a contraceptive. These rates of approximately 14% failure are comparable to poor use of the diaphragm and are only slightly better than rhythm as a contraceptive.
Pregnancy rates of barrier methods
There are very few large conventional prospective studies on the contraceptive efficacy of barrier methods published but the contraceptive efficacy of barrier methods that was found in two large retrospective surveys published in the USA in 1986 and 1989 are shown in Table 1. The pregnancy rates of non-barrier methods that were recorded in the studies are also shown. Of the three main methods, spermicide use alone had the highest failure rates.
The male condom
The published pregnancy rates for the male condom are summarized in Table 2. It can be seen in highly selected and motivated couples that the male condom has low and probably acceptable pregnancy rates of less than 5%.
The female condom
Although a number of different designs of device that can be inserted into the vagina to act as a barrier method for the whole of the vagina, cervix and part of the vulva have been described and in some cases patented, only one such device, Femidom, was commercially available at the end of 1992. The data on pregnancy rates have not yet been made available but they are thought to be similar to those of the male condom whilst laboratory studies have indicated that the plastic used in the device is impermeable to bacterial and viral sexually transmitted diseases.
Diaphragms and cervical caps
The published pregnancy rates for diaphragm and spermicide use as a contraceptive are summarized in Table 3. As with the male condom, diaphragms have low pregnancy rates in highly motivated women but in other groups, the rates are unacceptably high.
The cervical cap in its various designs has been studied in eight trials between 1982 and 1991, and pregnancy rates varied between 4.7 and 16.5% at one year of use.
Edited by Aldo Campana,