Cervical cap

The cervical cap is a cervical barrier type of birth control. It fits snugly over the cervix, the entrance of the uterus, and blocks sperm from entering the female reproductive tract. Cervical caps may be made out of latex or silicone.

Use
Anyone inserting or removing a cervical cap should first wash their hands, to avoid introducing harmful bacteria into the vaginal canal.

The cervical cap must be inserted sometime before sexual intercourse, and remain in the vagina for at least 8 hours after a man's last ejaculation. It is usually recommended to apply spermicide inside the cap, but some sources say spermicide use is optional. The cap must be removed within 72 hours (within 48 hours recommended in the U.S.) It should be washed with warm soapy water before storage.

Oil-based products should not be used with latex cervical caps. Lubricants or vaginal medications that contain oil will cause the latex to rapidly degrade and greatly increases the chances of the cap breaking or tearing.

Cervical caps should be replaced about every two years.

Types
Cavity rim caps adhere to the cervix. Prentif and Oves are cavity rim caps. Prentif is made of latex, and is available in sizes 22, 25, 28, and 31mm. Oves is a silicone, "disposable" cap that is replaced frequently. Unlike other caps, Oves adheres to the cervix by surface tension, rather than by suction. Some users may find the thinner walls of the Oves cap make it more comfortable. It is available in sizes 26, 28, and 30mm.

Other caps adhere to the vaginal walls around the cervix. The Dumas and Vimule caps are made of latex, while FemCap is made of silicone. Dumas, also called a vault cap, comes in five sizes: 50, 55, 60, 65, and 75mm. Vimule comes in three sizes: 42, 48, and 52mm. FemCap comes in three sizes: 22, 26, and 30mm. Each one of these devices fits differently over the cervix; a woman fitted for one type of cap cannot use that measurement as her size for a different type of cap.

There is also a larger cap-like device called the Lea's shield. This device is made of silicone, and designed to be one-size-fits-all.

Only Prentif, FemCap, and the Lea's shield are approved for use in the United States. Although other brands are available over-the-counter in some countries (and so over the internet), they may be confiscated by U.S. customs if imported into the country.

Fitting
Screening by a health care provider is necessary to determine if a cervical cap, or one brand of cap, is appropriate for a particular woman. If a cap is determined to be appropriate, the provider will also make a size determination.

Women who have given birth may have scar tissue or irregularly shaped cervixes that interfere with the cap adhering to the cervix or the nearby vaginal walls. Some women are good cadidates for caps even after vaginal birth, but an examination by an experienced provider is necessary to determine this.

Cavity rim caps are not appropriate for most women with an anteflexed uterus. This presentation of the cervix put such caps at high risk of being dislodged during intercourse. Women with anteflexed uteruses may still safely wear other types of caps.

Some women may not be able to wear a particular cap because it is not made in their size. The three to five sizes offered by cap manufacturers do not encompass the entire range of normal female anatomy.

Cervical caps should be refitted after any pregnancy. Although full-term vaginal delivery especially is likely to change the size a woman wears, changes to the cervix during pregnancy mean even women who experience miscarriage, or have a C-section should be refitted.

Obtaining a fitting appointment may be difficult for some women. A 1997 survey in the United States found that most family medicine residents had no experience with prescription methods of birth control other than oral contraceptives. In many countries, the cervical cap is the least common prescription method of birth control. A number of women in the Yahoo! DiaphragmsAndCaps group have reported their only route to obtaining a cervical cap was to purchase their own fitting kit, and take it to a doctor who had no previous experience fitting caps.

Effectiveness
The effectiveness of cervical caps, as of most forms of contraception, can be assessed two ways: method effectiveness and actual effectiveness. The method effectiveness is the proportion of couples correctly and consistently using the method who do not become pregnant. Actual effectiveness is the proportion of couples who intended that method as their sole form of birth control and do not become pregnant; it includes couples who sometimes use the method incorrectly, or sometimes not at all. Rates are generally presented for the first year of use. Most commonly the Pearl Index is used to calculate effectiveness rates, but some studies use decrement tables.

Cervical caps are not appropriate for 20-40% of women. It is not clear if such women were excluded from all studies of cap effectiveness, and some sources imply that appropriately fitted parous women (women who have given birth), especially, may experience lower failure rates than these studies imply.

Method effectiveness
Contraceptive Technology reports that the method failure rate of the cervical cap with spermicide is 9% per year for nulliparous women (women who have never given birth), and 26% per year for parous women. This appears to be based on a study of about 700 women using the Prentif cap.

In a multicenter trial involving 581 users of the Prentif cap, the method failure rate was 7% over two years. In a 1980s study of over three thousand users of the Prentif cap, the method failure rate was 4% per year.

Comparative trials with the diaphragm have found that the Prentif cap has a similar method failure rate as the diaphragm (which Contraceptive Technology reports as 6% per year). However, the FemCap was found to have a higher failure rate.

Actual effectiveness
For all forms of contraception, actual effectiveness is lower than method effectiveness, due to several factors: For instance, someone using a cervical cap might be fitted incorrectly by a health care provider, or by mistake remove the cap too soon after intercourse, or simply choose to have intercourse without placing the cap.
 * mistakes on the part of those providing instructions on how to use the method
 * mistakes on the part of the method's users
 * conscious user non-compliance with method.

The actual pregnancy rates among cap users vary depending on the population being studied, with yearly rates of 11% to 32% being reported.

History
The idea of blocking the cervix to prevent pregnancy is thousands of years old. Various cultures have used cervix-shaped devices such as oiled paper cones or lemon halves, or have made sticky mixtures that include honey or cedar rosin to be applied to the cervical opening. However, the modern idea of a cervical cap as a fitted device that seals itself against the vaginal walls is of much more recent origin.

In 1838, German gynecologist Friedrich Wilde created the first modern cervical cap by making custom-made rubber molds of their cervix for some of his patients. How many times these caps could be used is questionable, as uncured rubber degrades fairly quickly. An important precursor to the invention of more lasting caps was the rubber vulcanization process, patented by Charles Goodyear in 1844.

Over the next several decades, the cervical cap became the most widely used barrier contraceptive method in Western Europe and England. Although the diaphragm was always more popular in the U.S. than the cervical cap, the cap was also common.

A large number of types of cap were developed in the later nineteenth and early twentieth. Some of these caps are still available today. The Vimule cap has been available since at least 1927. The Prentif brand cap was introduced in the early 1930s. The Dumas cap was initially made of plastic and was available by the 1940s. (Lamberts (Dalston) Ltd., a U.K. company, manufacturers these three cap types.) Other types of caps had stems to hold them in place in the cervix; some of the stems actually extended into the uterus. These "stem pessaries" became precursors to the modern intrauterine device.

Use of all barrier methods, but especially cervical barriers, dropped dramatically after the 1960s introduction of the oral contraceptive pill and the intrauterine device. In 1976, the U.S. government enacted the Medical Device Amendment. This law required all manufacturers of medical devices to provide the FDA with data on the safety and efficacy of those devices. Lamberts (Dalston) Ltd., the only manufacturer at that time, failed to provide this information, and the FDA banned the use of cervical caps in the United States.

In the late 1970s, the FDA reclassified the cervical cap as an investigational device, and it regained very limited availability. Within a few years, the FDA withdrew investigational status from the Vimule cap because of a study that associated it with vaginal lacerations. In 1988, the Prentif cap gained FDA approval. The feminist movement played a large role in re-introducing the cervical cap to the U.S. One paper called its involvement at all steps of the FDA approval process "unprecedented."

Today, the cervical cap is one of the least common methods of contraception. Of sexually active American women, 0.6% are currently using either the cervical cap, contraceptive sponge, or female condom as their primary method of contraception, and fewer than 1% have ever used a cervical cap. Manufacturers, however, are bringing new products to market. The Oves cap became available in the U.K. in 2001, and the FDA approved the Lea's Shield in 2002 and the FemCap in 2003.