Birth control The effectiveness of<unk> s, as of most forms of contraception, can be assessed two ways. Perfect use or method effectiveness rates only include people who use<unk> s properly and consistently. Actual use, or typical use effectiveness rates are of all<unk>  users, including those who use<unk> s incorrectly or do not use<unk> s at every act of intercourse. 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. The typical use pregnancy rate among<unk>  users varies depending on the population being studied, ranging from 10 to 18% per year. The perfect use pregnancy rate of<unk> s is 2% per year.<unk> s may be combined with other forms of contraception (such as spermicide) for greater protection. Sexually transmitted infections A giant replica of a<unk>  on the Obelisk of Buenos Aires, Argentina, part of an awareness campaign for the 2005 World AIDS Day<unk> s are widely recommended for the prevention of sexually transmitted infections (STIs). They have been shown to be effective in reducing infection rates in both men and women. While not perfect, the<unk>  is effective at reducing the transmission of organisms that cause AIDS, genital herpes, cervical cancer, genital warts, syphilis, chlamydia, gonorrhea, and other diseases.<unk> s are often recommended as an adjunct to more effective birth control methods (such as IUD) in situations where STD protection is also desired. According to a 2000 report by the National Institutes of Health (NIH), consistent use of latex<unk> s reduces the risk of HIV transmission by approximately 85% relative to risk when unprotected, putting the seroconversion rate (infection rate) at 0.9 per 100 person-years with<unk> , down from 6.7 per 100 person-years. Analysis published in 2007 from the University of Texas Medical Branch and the World Health Organization found similar risk reductions of 80–95%. The 2000 NIH review concluded that<unk>  use significantly reduces the risk of gonorrhea for men. A 2006 study reports that proper<unk>  use decreases the risk of transmission of human papillomavirus (HPV) to women by approximately 70%. Another study in the same year found consistent<unk>  use was effective at reducing transmission of herpes simplex virus-2, also known as genital herpes, in both men and women. Although a<unk>  is effective in limiting exposure, some disease transmission may occur even with a<unk> . Infectious areas of the genitals, especially when symptoms are present, may not be covered by a<unk> , and as a result, some diseases like HPV and herpes may be transmitted by direct contact. The primary effectiveness issue with using<unk> s to prevent STDs, however, is inconsistent use.<unk> s may also be useful in treating potentially precancerous cervical changes. Exposure to human papillomavirus, even in individuals already infected with the virus, appears to increase the risk of precancerous changes. The use of<unk> s helps promote regression of these changes. In addition, researchers in the UK suggest that a hormone in semen can aggravate existing cervical cancer,<unk>  use during sex can prevent exposure to the hormone. Causes of failure<unk>  fitting in size over a penis made of silicone<unk> s may slip off the penis after ejaculation, break due to improper application or physical damage (such as tears caused when opening the package), or break or slip due to latex degradation (typically from usage past the expiration date, improper storage, or exposure to oils). The rate of breakage is between 0.4% and 2.3%, while the rate of slippage is between 0.6% and 1.3%. Even if no breakage or slippage is observed, 1–3% of women will test positive for semen residue after intercourse with a<unk> . Failure rates are higher for anal sex, and until 2022,<unk> s were only approved by the FDA for vaginal sex. The One Male<unk>  received FDA approval for anal sex on February 23, 2022. "Double bagging", using two<unk> s at once, is often believed to cause a higher rate of failure due to the friction of rubber on rubber. This claim is not supported by research. The limited studies that have been done found that the simultaneous use of multiple<unk> s decreases the risk of<unk>  breakage. Different modes of<unk>  failure result in different levels of semen exposure. If a failure occurs during application, the damaged<unk>  may be disposed of and a new<unk>  applied before intercourse begins – such failures generally pose no risk to the user. One study found that semen exposure from a broken<unk>  was about half that of unprotected intercourse; semen exposure from a slipped<unk>  was about one-fifth that of unprotected intercourse. Standard<unk> s will fit almost any penis, with varying degrees of comfort or risk of slippage. Many<unk>  manufacturers offer "snug" or "magnum" sizes. Some manufacturers also offer custom sized-to-fit<unk> s, with claims that they are more reliable and offer improved sensation/comfort. Some studies have associated larger penises and smaller<unk> s with increased breakage and decreased slippage rates (and vice versa), but other studies have been inconclusive. It is recommended for<unk> s manufacturers to avoid very thick or very thin<unk> s, because they are both considered less effective. Some authors encourage users to choose thinner<unk> s "for greater durability, sensation, and comfort", but others warn that "the thinner the<unk> , the smaller the force required to break it". Experienced<unk>  users are significantly less likely to have a<unk>  slip or break compared to first-time users, although users who experience one slippage or breakage are more likely to suffer a second such failure. An article in Population Reports suggests that education on<unk>  use reduces behaviors that increase the risk of breakage and slippage. A Family Health International publication also offers the view that education can reduce the risk of breakage and slippage, but emphasizes that more research needs to be done to determine all of the causes of breakage and slippage. Among people who intend<unk> s to be their form of birth control, pregnancy may occur when the user has sex without a<unk> . The person may have run out of<unk> s, or be traveling and not have a<unk>  with them, or simply dislike the feel of<unk> s and decide to "take a chance". This type of behavior is the primary cause of typical use failure (as opposed to method or perfect use failure). Another possible cause of<unk>  failure is sabotage. One motive is to have a child against a partner's wishes or consent. Some commercial sex workers from Nigeria reported clients sabotaging<unk> s in retaliation for being coerced into<unk>  use. Using a fine needle to make several pinholes at the tip of the<unk>  is believed to significantly impact on their effectiveness. Cases of such<unk>  sabotage have occurred.
Condom
Vaginal syringe
Vaginal ring
Macy catheter
Dental dam
Word catheter
Hot water bottle
Antimonial cup