Contraceptives

Overview: An overview of different contraceptive methods, and their utility for preventing unwanted pregnancies, and, to a lesser extent, sexually transmitted diseases.

Contraceptives

Each method of birth control has a failure rate--an inability to prevent pregnancy over a one-year period. Sometimes the failure rate is due to the method and sometimes it is due to human error, such as incorrect use or not using it at all. Each method has possible side effects, some minor and some serious. Some methods require lifestyle modifications, such as remembering to use the method with each and every sexual intercourse. Some cannot be used by individuals with certain medical problems. Most forms of contraception can be split into two groups: the physical, or barrier methods, and the chemical methods. Different forms of contraception can also be combined.

There are five barrier methods of contraception: male condoms, female condoms, diaphragm, sponge, and cervical cap. In each instance, the method works by keeping the sperm and egg apart. Usually, these methods have only minor side effects. The main possible side effect is an allergic reaction either to the material of the barrier or the spermicides that should be used with them. Using the methods correctly for each and every sexual intercourse gives the best protection. For many people, the prevention of sexually transmitted diseases (STDs), including HIV (human immunodeficiency virus), which leads to AIDS, is a factor in choosing a contraceptive. Only one form of birth control currently available--the latex condom, worn by the man--is considered highly effective in helping protect against HIV and other STDs.

A male condom is a sheath that covers the penis during sex. Condoms on the market at press time were made of either latex rubber or natural skin (also called "lambskin" but actually made from sheep intestines). Of these two types, only latex condoms have been shown to be highly effective in helping to prevent STDs. Latex provides a good barrier to even small viruses such as human immunodeficiency virus and hepatitis B. Each condom can only be used once. Condoms have a birth control failure rate of about 15 percent. Most of the failures can be traced to improper use. (Hatcher, 1998).

The Reality Female Condom was approved by FDA in April 1993. It consists of a lubricated polyurethane sheath with a flexible polyurethane ring on each end. One ring is inserted into the vagina much like a diaphragm, while the other remains outside, partially covering the labia. The female condom may offer some protection against STDs, but for highly effective protection, male latex condoms must be used. (The female condom should not be used at the same time as the male condom because they will not both stay in place.) In a six-month trial, the pregnancy rate for the Reality Female Condom was about 13 percent. The estimated yearly failure rate ranges from 21 to 26 percent. (Hatcher, 1998).

The contraceptive sponge, approved by FDA in 1983, is made of white polyurethane foam. The sponge, shaped like a small doughnut, contains the spermicide nonoxynol-9. Like the diaphragm, it is inserted into the vagina to cover the cervix during and after intercourse. It does not require fitting by a health professional and is available without prescription. It is to be used only once and then discarded. The failure rate is between 18 and 28 percent. (Hatcher, 1998) An extremely rare side effect is toxic shock syndrome (TSS), a potentially fatal infection caused by a strain of the bacterium Staphylococcus aureus and more commonly associated with tampon use.

The diaphragm is a flexible rubber disk with a rigid rim. Diaphragms range in size from 2 to 4 inches in diameter and are designed to cover the cervix during and after intercourse so that sperm cannot reach the uterus. Spermicidal jelly or cream must be placed inside the diaphragm for it to be effective. The diaphragm must be fitted by a health professional and the correct size prescribed to ensure a snug seal with the vaginal wall. If intercourse is repeated, additional spermicide should be added with the diaphragm still in place. The diaphragm should be left in place for at least six hours after intercourse. The diaphragm used with spermicide has a failure rate of from 6 to 18 percent. (Hatcher, 1998).

The cervical cap, approved for contraceptive use in the United States in 1988, is a dome-shaped rubber cap in various sizes that fits snugly over the cervix. Like the diaphragm, it is used with a spermicide and must be fitted by a health professional. It is more difficult to insert than the diaphragm, but may be left in place for up to 48 hours. In addition to the allergic reactions that can occur with any barrier method. 5.2 to 27 percent of users in various studies have reported an unpleasant odor and/or discharge. There also appears to be an increased incidence of irregular Pap tests in the first six months of using the cap, and TSS is an extremely rare side effect. The cap has a failure rate of about 18 percent.

Then there are the chemical methods, which eliminate ovulation or prevent implantation of a fertilized egg into the placenta wall. There are two types of birth control pills: combination pills, which contain both estrogen and a progestin (a natural or synthetic progesterone), and "mini-pills," which contain only progestin. The combination pill prevents ovulation, while the mini-pill reduces cervical mucus and causes it to thicken. This prevents the sperm from reaching the egg. Also, progestins keep the endometfium (uterine lining) from thickening. This prevents the fertilized egg from implanting in the uterus. The failure rate for the mini-pill