Barrier Methods of contraception
Barrier methods of contraception include the condom, diaphragm, cervical cap, and vaginal spermicides.
The male condom offers the most effective method of preventing sexually transmitted infections. Male condoms are manufactured from latex, lamb caecum, or polyurethane. All prevent pregnancy. Naturally membrane condoms do not offer the same protection against sexually transmitted disease. Small pores may permit the passage of viruses, including HIV, hepatitis B, and HSV.
Polyurethane condoms may be used for patients with latex allergies. With latex condoms, only water-based lubricants (KY jelly, spermicidal agents) should be used. Oil based lubricants (lotion, petroleum jelly, massage oil) may damage the condom.
The failure rate with condom use the first year is 3% with perfect use and 14% with typical use. Failures occur more commonly because condoms are not used with every act of intercourse, rather than from slippage or breakage. The advantages of condom use include protection from STDs, low cost accessibility, and lack of side effects. All patients at risk for sexually transmitted infections should be counseled to use condoms. The first female condom, call Reality, was approved by the FDA in 1993.
Vaginal spermicides are used with the diaphragm and cervical cap. They may be used alone, but have a wide range of failure rates, from 5-50% in the first year. Spermicides consist of a base (gel, foam, cream, film, and suppository) and an active chemical agent which kill sperms (nonoxynol-9) in the United States).
Suppositories and film must be placed at least 15 minutes before intercourse to allow adequate dispersion. Spermicides might slightly decrease the risk of sexually transmitted infection (by approximately 25%). The advantages of spermicides are their accessibility, ease of use, and ability to augment other forms of contraception. They are not good options if a patient is allergic to the base or spermicidal agent or if she has abnormal vaginal anatomy (such as a septum).
The diaphragm is a dome shaped cup that rests between the pubic symphysis and in the posterior fornix. Diaphragms are manufactured in different sizes, from 50 mm to 95 mm. A patient should be fitted with the largest size that is comfortable. The diaphragm is used with a spermicidal cream or jelly. It may be placed up to 6 hours before intercourse, should be left in place for at least 6 hours before intercourse, and should not be worn more than 24 hours total. A diaphragm should be refitted after a weight gain or loss of 10 pounds and postpartum. The diaphragm has a 20% failure rate with typical use, a 6% failure rate with perfect use over the first year.
The cervical cap
The cervical cap is as smaller that fits snugly over the cervix. The cervical cap is manufactured in 4 sizes. Because of the limited number of sizes, 6-10% of women are unable to be fitted properly. The cap may be left in place for up to 48 hours total, and should be left in place for at least 6 hours after intercourse. It also is used with a spermicidal preparation. The cervical cap is more efficacious in nulliparous women. The failure rate is 20% for typical use, 9% for perfect use in nulliparous women. In parous women the failure rate is 40% for typical use, 26% for perfect use.
The advantages of the diaphragm and cervical cap include a lack of systemic side effects and potential protection against STDs. They are good choices for women who need contraception intermittently. They should be used with caution in women who have allergies to latex or spermicides, vaginal anatomy abnormalities, a history of Toxic Shock Syndrome, or recurrent urinary tract infections.