Contraception |
|
|
INTRODUCTION | ¡@ |
The practice of contraception is as old as human existence. For centuries, humans have relied upon their imagination to avoid pregnancy. Ancient writings noted on Kahun papyrus dating to 1850 BC refer to contraceptive techniques using a vaginal pessary of crocodile dung and fermented dough, which most likely created a hostile environment for sperm. The Kahun papyrus also refers to vaginal plugs of gum, honey, and acacia. Soranus of Ephesus during the early second century in Rome created a highly acidic concoction of fruits, nuts, and wool that was placed at the cervical os to create a spermicidal barrier.
Today, the voluntary control of fertility is of paramount importance to modern society. From a global perspective, countries currently face the crisis of rapid growth of the human population that has begun to threaten human survival. At the present rate, the population of the world will double in 40 years; in several of the more socioeconomically disadvantaged countries, the populations will double in less than 20 years.
On a smaller scale, effective control of reproduction can be essential to a woman's ability to achieve her own individual goals as well as contribute to her sense of well-being. A patient's choice of contraceptive method involves factors such as efficacy, safety, noncontraceptive benefits, cost, and personal considerations. This article discusses the predominant modes of contraception used in the United States, along with the safety, efficacy, advantages, disadvantages, and noncontraceptive benefits of each.
|
|
PERIODIC ABSTINENCE | ¡@ |
Coitus interruptus
Coitus interruptus involves withdrawal of the entire penis from the vagina before ejaculation. Fertilization is prevented by lack of contact between spermatozoa and the ovum. This method of contraception remains a significant means of fertility control in the developing world.
Efficacy: Effectiveness depends largely on the man's capability to withdraw prior to ejaculation. The failure rate is estimated to be approximately 4% in the first year of perfect use. In typical use, the rate is approximately 19% during the first year of use.
Advantages: Advantages include immediate availability, requires no devices, no cost, does not involve chemicals, and theoretical reduced risk of transmission of sexually transmitted diseases (STDs).
Disadvantages: A high probability of pregnancy exists with incorrect or inconsistent use.
Lactational amenorrhea
Elevated prolactin levels and a reduction of gonadotropin-releasing hormone from the hypothalamus during lactation suppress ovulation. This leads to a reduction in luteinizing hormone (LH) release and inhibition of follicular maturation. The duration of this suppression varies and is influenced by the frequency and duration of breastfeeding and the length of time since birth. Ovulation usually returns after 6 months despite continuous nursing.
Efficacy: Perfect use failure rate within the first 6 months is 0.5%. Typical use failure rate within the first 6 months is 2%.
Advantages: Involution of the uterus occurs more rapidly. Menses are suppressed. This method can be used immediately after childbirth. This method facilitates postpartum weight loss.
Disadvantages: Return to fertility is uncertain. Frequent breastfeeding may be inconvenient. This method should not be used if the mother is HIV positive.
Natural family planning
Natural family planning is one of the most widely used methods of fertility regulation, particularly for those whose religious or cultural beliefs do not permit devices or drugs for contraception. This method involves periodic abstinence, with couples attempting to avoid intercourse during a woman's fertile period¡Xaround the time of ovulation. Techniques to determine the fertile period include the calendar method, cervical mucus method, or the symptothermal method.
The calendar method is based on 3 assumptions as follows: (1) A human ovum is capable of fertilization only for about 24 hours after ovulation, (2) spermatozoa can retain their fertilizing ability for only 48 hours after coitus, and (3) ovulation usually occurs 12-16 days before the onset of the subsequent menses. The menses is recorded for 6 cycles to approximate the fertile period. The earliest day of the fertile period is determined by the number of days in the shortest menstrual cycle subtracted by 18. The latest day of the fertile period is calculated by the number of days in the longest cycle subtracted by 11.
With the cervical mucus method, the woman attempts to predict her fertile period by quantifying the cervical mucus with her fingers. Under the influence of estrogen, the mucus increases in quantity and becomes progressively more elastic and copious until a peak day is reached. This is followed by a scant and dry mucus, secondary to the influence of progesterone, which remains until the onset of the next menses. Intercourse is allowed 4 days after the maximal cervical mucus until menstruation.
The symptothermal method predicts the first day of abstinence by either utilizing the calendar method or the first day mucus is detected, whichever is noted first. The end of the fertile period is predicted by use of basal body temperature. The basal body temperature of a woman is relatively low during the follicular phase and rises in the luteal phase of the menstrual cycle in response so the thermogenic effect of progesterone. The rise in temperature can vary from 0.2-0.5°C. The elevated temperatures begin 1-2 days after ovulation and correspond to the rising level of progesterone. Intercourse can resume 3 days after the temperature rise.
Efficacy: The failure rate in typical use is estimated to be approximately 25%.
Advantages: No adverse effects from hormones occur. This may be the only method acceptable to couples for cultural or religious reasons. Immediate return of fertility occurs with cessation of method.
Disadvantages: This is most suitable for women with regular and predictable cycles. Complete abstinence is necessary during the fertile period unless backup contraception is utilized. This method requires discipline. The method is not effective with improper use. A relatively high failure rate exists. This method does not protect against STDs.
|
|
MECHANICAL BARRIERS | ¡@ |
Male condom
The condom consists of a thin sheath placed over the glans and the shaft of the penis that is applied before any vaginal insertion. It is one of the most popular mechanical barriers. Among all of the barrier methods, the condom provides the most effective protection of the genital tract from STDs. Its usage has increased from 13.2-18.9% among all women of reproductive age because of the concern regarding the acquisition of HIV and STDs. It prevents pregnancy by acting as a barrier to the passage of semen into the vagina
Efficacy: The failure rate of condoms in couples that use them consistently and correctly during the first year of use is estimated to be about 3%. However, the true failure rate is estimated to be about 14% during the first year of typical use. This marked difference of failure rates reflects the error of usage. Common errors with condoms usage include failure to use condoms with every act of intercourse and throughout intercourse, improper lubricant use with latex condoms (eg, oil-based lubricants), incorrect placement of the condom on the penis, and poor withdrawal technique.
Advantages: Condoms are readily available and usually are inexpensive. This method involves the male partner in the contraceptive choice. Condoms are effective against both pregnancy and STDs.
Disadvantages: Condoms possibly decrease enjoyment of sex. Some users may have a latex allergy. Condom breakage and slippage decrease effectiveness. Oil-based lubricants may damage the condom.
Female condom
The Reality female condom is a polyurethane sheath intended for 1-time use, similar to the male condom. It contains 2 flexible rings and measures 7.8 cm in diameter and 17 cm long. The ring at the closed end of the sheath serves as an insertion mechanism and internal anchor that is placed inside the vaginal canal. The other ring forms the external patent edge of the device and remains outside of the canal after insertion.
The female condom prevents pregnancy by acting as a barrier to the passage of semen into the vagina. Simultaneous use of both the female and male condom is not recommended because they may adhere to each other, leading to slippage or displacement of either device.
Efficacy: Efficacy trials are noted to be limited. Initial trials have demonstrated a pregnancy rate of 15% in 6 months. The proportion of women using this method of contraception in the United States is less than 1%.
Advantages: The female condom provides some protection to the labia and the base of the penis during intercourse. The sheath is coated on the inside with a silicone-based lubricant. It does not deteriorate with oil-based lubricants. It can be inserted as long as 8 hours before intercourse.
Disadvantages: The lubricant does not contain spermicide. The device is difficult to place in the vagina. The inner ring may cause discomfort. Some users consider the female condom cumbersome. The female condom may cause urinary tract infection (UTI) if left in vagina for a prolonged period.
Diaphragm
The diaphragm is a shallow latex cup with a spring mechanism in its rim to hold it in place in the vagina. Diaphragms are manufactured in various diameters. A pelvic examination and measurement of the diagonal length of the vaginal canal determines the correct diaphragm size. It is inserted before intercourse so that the posterior rim fits into the posterior fornix and the anterior rim is placed behind the pubic bone. Spermicidal cream or jelly is applied to the inside of the dome, which then covers the cervix.
It prevents pregnancy by acting as a barrier to the passage of semen into the cervix. Once in position, the diaphragm provides effective contraception for 6 hours. If a longer interval has elapsed without removal of the diaphragm, a fresh spermicide is added with an applicator. After intercourse, the diaphragm must be left in place for at least 6 hours.
Efficacy: Effectiveness of the diaphragm depends on the age of the user, experience with its use, continuity of use, and the use of spermicide. Typical use failure rate within the first year is estimated to be 20%.
Advantages: The diaphragm does not entail hormonal usage. Contraception is controlled by the woman. The diaphragm may be placed by the woman in anticipation of intercourse.
Disadvantages: Prolonged use during multiple acts of intercourse may increase the risk of UTIs. Usage for longer than 24 hours is not recommended due to the possible risk of toxic shock syndrome. The diaphragm requires professional fitting. Poorly fitted diaphragms may cause vaginal erosions. Diaphragms have a high failure rate. Use of a diaphragm requires brief formal training. The diaphragm may develop odor if not properly cleansed.
Cervical cap
The cervical cap is a cup-shaped latex device that fits over the base of the cervix. A groove along the inner circumference of the rim improves the seal between the inner rim of the cap and the base of the cervix. Spermicide is needed to fill the cap one third full prior to its insertion. It is inserted as long as 8 hours before coitus and can be left in place for as long as 48 hours.
A cervical cap acts as both a mechanical barrier to sperm migration into the cervical canal and as a chemical agent with the use of spermicide.
Efficacy: The effectiveness depends on the parity of women due to the shape of the cervical os. With perfect use in the first year, the nulliparous woman's failure rate is 9%, as opposed to 20% in the parous woman. With typical use within the first year, the failure rate is 20% in the nulliparous woman and 40% in the parous woman.
Advantages: It provides continuous contraceptive protection for its duration of use regardless of the number of intercourse acts. Additional spermicide, unlike the diaphragm, is not necessary for repeated intercourse. The cervical cap does not involve ongoing use of hormones.
Disadvantages: Cervical erosion may lead to vaginal spotting. A theoretical risk of toxic shock syndrome exists if the cervical cap is left in place longer than the prescribed period. The cervical cap requires professional fitting and training for use. Severe obesity may make placement difficult. A relatively high failure rate exists. Candidates must have history of normal results on pap smears.
Spermicidal agents
Vaginal spermicides consist of a base combined with either nonoxynol-9 or octoxynol. The actual spermicidal agent consists of a surfactant that destroys the sperm cell membrane. Bases include vaginal foams, suppositories, jellies, films, foaming tablets, and creams. These have to be inserted into the vagina prior to each coital act. Use of spermicidal agents also reduces the risk of infection by both viral and bacterial STDs; however, clinical data on its efficacy on preventing the transmission of HIV are limited. Nonoxynol-9 is toxic to the lactobacilli that are part of the normal vaginal flora. Adverse effects include an increased vaginal colonization with the bacteria Escherichia coli that may predispose to bacteriuria after intercourse.
Spermicides prevent sperm from entering the cervical os by attacking the sperm's flagella and body, reducing their mobility, and disrupting their fructolytic activity, thereby inhibiting their nourishment.
Efficacy: Perfect use failure rate within the first year is 6%. Typical use failure rate within the first year is 26%.
Advantages: The lubrication provided by spermicides may heighten satisfaction in both partners. Another advantage is the ease of application. Either partner can purchase and apply spermicide because it is easily accessible, available over the counter, and inexpensive. Applying spermicide requires minimal patient education. It augments contraceptive efficacy of the cervical cap and diaphragm. Spermicides produce no systemic adverse effects.
Disadvantages: Spermicides provide minimal protection from STDs. Insertion may be uncomfortable for some couples. Vaginal irritation is possible, and spermicide may cause allergic reaction.
|
|
HORMONAL CONTRACEPTIVES | ¡@ |
Implant
The US Food and Drug Administration (FDA) approved the contraceptive use of levonorgestrel implants (Norplant) in 1990. This method consists of 6 silicone rubber rods, each measuring 34 mm long and 2.4 mm in diameter and each containing 36 mg of levonorgestrel. The implant releases approximately 80 mcg of levonorgestrel per 24 hours during the first year of use, achieving effective serum concentrations of 0.4-0.5 ng/mL within the first 24 hours. The rate of release decreases to an average of 30 mcg/d in the latter years of use. Release of the progestational agent by diffusion provides effective contraception for 5 years. Contraceptive protection begins within 24 hours of insertion if inserted during the first week of the menstrual cycle. The rods are inserted subcutaneously, usually in the woman's upper arm, where they are visible under the skin and can be palpated easily.
The mechanism of action is a combination of suppression of the LH surge, suppression of ovulation, development of viscous and scant cervical mucus to deter sperm penetration, and prevention of endometrial growth and development.
Efficacy: The contraceptive efficacy of the method is equivalent to that of surgical sterilization. Overall, pregnancy rates increase from 0.2% in the first year to 1.1% by the fifth year.
Advantages: The longevity of its effectiveness is an advantage. Its effectiveness is not related to its use in regards to coitus. Exogenous estrogen is absent. Prompt return to the previous state of fertility occurs upon removal. No adverse effect on breast milk production occurs.
Disadvantages: A minor surgical procedure is necessary for incision. Difficulty in removal is a disadvantage. Menstrual irregularities are common along with other adverse effects, including weight gain, headaches, mood changes, hirsutism, galactorrhea, and acne.
Absolute contraindications include active thrombophlebitis or thromboembolic disease, undiagnosed genital bleeding, acute liver disease, benign or malignant liver tumors, known or suspected breast cancer, and history of idiopathic intracranial hypertension. Relative contraindications include heavy cigarette smoking, history of ectopic pregnancy, diabetes mellitus, hypercholesterolemia, severe acne, hypertension, history of cardiovascular disease, severe vascular or migraine headaches, and severe depression.
Appropriate candidates are women who are postpartum or breastfeeding, women who have difficulty with contraceptive compliance, women in whom pregnancy is contraindicated due to medical condition, and patients with contraindications for use of estrogen.
The only other FDA approved implant is the 2-rod levonorgestrel system, Norplant II. Each rod is 4.4 cm long and contains a cured homogenous mixture of the drug and a polydimethylsiloxane elastomer covered by silicone tubing. Norplant II is approved for 3 years of use but has been shown to be effective for as long as 5 years. Studies have shown Norplant II to have release rates, pregnancy rates, and side effect profiles similar to Norplant.
Injectable depomedroxyprogesterone acetate
Depomedroxyprogesterone acetate (DMPA) is a suspension of microcrystals of a synthetic progestin that is injected intramuscularly. Pharmacological active levels are achieved within 24 hours after injection, and serum concentrations of 1 ng/mL are maintained for 3 months. During the fifth or sixth month after injection, the levels decrease to 0.2 ng/mL, and they become undetectable by 7-9 months after injection.
DMPA acts by the inhibition of ovulation with the suppression of follicle-stimulating hormone (FSH) and LH levels and eliminates the LH surge. This results in a relative hypoestrogenic state. Single doses of 150 mg will suppress ovulation in most women for as long as 14 weeks. The contraceptive regimen consists of 1 dose every 3 months.
Efficacy: DMPA is an extremely effective contraceptive option. Neither varying weight nor use of concurrent medications has been noted to alter efficacy. Within the first year of use, the failure rate is 0.3%.
Advantages: DMPA does not produce the serious adverse effects of estrogen, such as thromboembolism. Diminished anemia occurs. Dysmenorrhea is decreased. Risk of endometrial and ovarian cancer is decreased.
Disadvantages: Disruption of the menstrual cycle to eventual amenorrhea occurs in 50% of women within the first year. Persistent irregular bleeding can be treated by administering the subsequent dose earlier or by adding a low-dose estrogen temporarily. Because DMPA persists in the body for several months in women who have used it on a long-term basis, it can delay the return to fertility. Approximately 70% of former users desiring pregnancy conceive within 12 months, and 90% of former users conceive within 24 months. Similar to the delay in fertility after discontinuation of DMPA, other adverse effects, such as weight gain, depression, and menstrual irregularities, may continue for as long as 1 year after the last injection. Recent studies in the literature have investigated a possible link between DMPA and bone density loss. Results are conflicting and limited.
Injectable medroxyprogesterone acetate and estradiol combination
One of the newest developments in contraception is a combined injectable contraception (Lunelle). A single injection of medroxyprogesterone acetate and estradiol combination (MPA/EC) contains medroxyprogesterone and estradiol cypionate. It recently received FDA approval in the United States and is marketed as a single-use ampule of an aqueous suspension of the 2 hormones. In contrast to DMPA, it contains estrogen and is administered monthly.
Its mechanism of action is similar to oral contraceptives (OCs) in that it suppresses ovulation.
Efficacy: The contraceptive efficacy and tolerability of MPA/EC was established in 15,614 women who participated in trials conducted by the World Health Organization (WHO). One-year failure rates of less than 1% have been reported in the WHO clinical trials. In a 60-week US multicenter study of 782 women, 1 year of use did not demonstrate any pregnancies.
Advantages: Unlike DMPA, earliest return of ovulation with multiple monthly injections is approximately 60 days after the last injection. Adequate contraception protection occurs regardless of body weight. Return to fertility is 53% and 83% within 6 months and 8 months, respectively. Regular menses occur, with average cycle of 28 days. Dysmenorrhea and menorrhagia decrease. MPA/EC does not demonstrate clinical changes in lipid metabolism. MPA/EC does not appear to cause procoagulant changes.
Disadvantages: Disadvantages include irregular spotting, weight gain, possible decrease in libido, and mild depression. In contrast to other hormonal contraceptive methods, due to its novelty, epidemiological studies and data in regards to cancer risks are limited. More extensive worldwide use and additional studies may demonstrate the risk, if any, on cancer of the reproductive tract. At this point, a theoretical protection of ovarian and endometrial cancers as demonstrated in oral combination contraceptives exists.
Progestin-only oral contraceptive
Progestin-only oral contraceptives, also known as the minipill, are not used widely in the United States. Fewer than 1% of users of oral contraceptives utilize them as their sole method of contraception. Candidates for use include women who are breastfeeding and women with contraindications to estrogen use. Two formulations are available, both of which have lower doses of progestin than combined OCs. One formulation contains 75 mcg of norgestrel. The other has 350 mcg of norethindrone.
Prevention of contraception involves a combination of mechanisms similar to, but not as efficacious as, combination OCs. Mechanisms of action include the following: suppression of ovulation (not uniformly in all cycles); variable dampening effect on the midcycle peaks of LH and FSH; increase in cervical mucus viscosity by reduction in its volume and alteration of its structure; reduction in the number and size of endometrial glands, leading to an atrophic endometrium not suitable for ovum implantation; and reduction in cilia motility in the fallopian tube, thus slowing the rate of ovum transport.
Efficacy: Serum progestin levels peak approximately 2 hours after administration. Within 24 hours, rapid distribution and elimination returns the level to baseline. Greater efficacy is achieved with consistent administration. Failure rates with typical use are estimated to be 7% in the first year of use. However, any variation can increase the failure rate.
Advantages: Due to the lack of estrogen, minimal evidence exists that demonstrates the serious complications to which estrogen can contribute (ie, thromboembolism). Noncontraceptive benefits include decreased dysmenorrhea, decreased menstrual blood loss, and decreased premenstrual syndrome (PMS) symptoms. Unlike DMPA, fertility is immediately reestablished after the cessation of Progestin-only oral contraceptives.
Disadvantages: The most significant disadvantage is the continuous need for compliance with regularity of usage. Users need to be counseled on the need for a backup method of contraception if a pill is missed or taken late. A pill is considered late if ingestion occurs 3 hours after the established time of administration. If a pill is missed, it should be taken as soon as possible, the next pill is to be taken at the scheduled time. Backup contraception should be utilized for the next 48 hours. Adverse effects include nausea, breast tenderness, headache, menstrual irregularities, and amenorrhea.
Combination oral contraceptives
OCs have been marketed in the United States since 1962. The dose of sex steroids has declined significantly in the past 40 years. Prior to 1992, the estrogenic component of OCs consisted of either ethinyl estradiol or mestranol. Today, ethinyl estradiol is used in all preparations containing 35 mcg or less of estrogen in the United States. The progestin component consists of norethindrone, levonorgestrel, norgestrel, norethindrone acetate, or ethynodiol diacetate. Recently, 2 new progestins have been added, norgestimate and desogestrel.
The other major new development is the reduction in the dosage of ethinyl estradiol to 20 mcg. The major impetus for this change is to improve the safety and reduce side effects. However, little data exist to indicate whether reduction of the estrogen dose is associated with a decreased risk of serious sequelae. These lower doses are associated with a decrease in the incidence of estrogen-related adverse effects, such as weight gain, breast tenderness, and nausea.
In the United States today, over 30 OC formulations exist. Monophasic OCs have a constant dose of both estrogen and progestin in each of the hormonally active pills. Phasic combinations can alter either or both hormonal components. Use should be initiated either on the first day of the menses or the first Sunday after menses has begun. The majority of the formulations have 21 hormonally active pills followed by 7 placebo pills. This facilitates consistent daily pill intake.
If a woman misses 1 or 2 pills, she should take 1 tablet as soon as it is remembered. She then takes 1 tablet twice daily until each of the missed pills has been accounted for. Women who have missed more than 2 consecutive pills should be advised to use a backup method of contraception simultaneous to finishing up the packet of pills until their next menses.
Prevention of ovulation is considered the dominant mechanism of action. Either estrogen or progesterone alone is capable of inhibiting both FSH and LH sufficiently to prevent ovulation. The combination of the 2 steroids creates a synergistic effect that greatly increases their antigonadotropic and ovulation inhibitory effect. They also alter the consistency of cervical mucous, affect the endometrial lining, and alter tubal transport.
Efficacy: Failure rates are associated with individual compliance. Rates range from 0.1% with perfect use to 5% with typical use.
Advantages: OCs are used as treatment for menstrual irregularity because menses is more regular and predictable. In the prevention of ovulation, OCs can reduce and sometimes eliminate mittelschmerz. Women with anemia secondary to menorrhagia increase their iron stores. Women can manipulate the cycle to avoid menses during certain events, such as vacations or weekends by extending the number intake days of hormonally active pills or by skipping the placebo pill week. OCs prevent benign conditions, such as benign breast disease, pelvic inflammatory disease (PID), and functional cysts. Functional cysts are reduced by the suppression of stimulation of the ovaries by FSH and LH. Ectopic pregnancies are prevented by the cessation of ovulation.
OCs are noted to prevent epithelial ovarian and endometrial carcinoma. Studies have noted an approximate 40% reduced risk of malignant and borderline ovarian epithelial cancer. This protection appears to last for at least 15 years following discontinuation of use and increases with duration of use. This protection has not been studied with low-dose OCs and/or in women with genetic ovarian cancer syndromes. Use of OCs is associated with a 50% reduction of risk of endometrial adenocarcinoma. Protection appears to persist for at least 15 years following discontinuation of use.
Disadvantages: Adverse effects include nausea, breast tenderness, weight gain, breakthrough bleeding, amenorrhea, headaches, depression, anxiety, and decreased libido. OCs do not provide protection from STDs. Daily administration is necessary, and inconsistent use may increase the failure rate. A few months of delay of normal ovulatory cycles after discontinuation of OCs may occur. Women who continue to have amenorrhea after a discontinuation period of 6 months require a full evaluation.
¡@
¡@
¡@
¡@
¡@
¡@
¡@
¡@
Contraindications to use include history of deep vein thrombosis, pulmonary embolism, or congestive heart failure; cerebrovascular disease or coronary artery disease; untreated hypertension; diabetes with vascular complications; estrogen-dependent neoplasia; breast cancer; undiagnosed abnormal vaginal bleeding; known or suspected pregnancy; active liver disease; and age older than 35 years and cigarette smoking.
|
|
INTRAUTERINE DEVICES | ¡@ |
Although the intrauterine device (IUD) is a highly effective method of contraception, it is used by less than 2% of American women of reproductive age. The reason for such a small percentage stems from the withdrawal of FDA-approved IUDs in the 1970s. The Dalkon Shield IUD was withdrawn due to the series of litigations related to septic abortion deaths. The manufacturers withdrew their product due to the decision that the cost of defending the litigation suits was deemed too expensive.
Until as recently as last year, the only 2 IUDs available in the United States were the Copper T380 and the progesterone-releasing form. In December 2000, the FDA approved another form of IUD, the levonorgestrel intrauterine system (LNG IUS, Mirena). Over 2 million women in Europe have used this form of contraception in the past decade with great success.
Description
The T-shaped progesterone-releasing IUD, which is placed into the uterine cavity, is made of ethylene vinyl acetate copolymer. It contains 38 mg of progesterone and minimal amounts of barium sulfate for greater visibility on x-rays. The vertical limbs are 36 mm long and the horizontal arms are 32 mm wide. It has a pair of dark blue double strings that hangs from the lower limb. Approximately 65 mcg of progesterone a day is released from the progesterone form from a reservoir in its stem. This is a sufficient amount of hormone to last for 400 days; therefore, this IUD must be replaced yearly.
The Copper T380 was introduced in 1988. The T-shaped IUD is made of polyethylene with fine copper wire wrapped around the vertical stem. The string is clear or white and hangs from the lower limb of the IUD. This device consists of 308 mg of copper covering portions of its stem and arms. Contraceptive effectiveness continues for 10 years, after which time it must be replaced.
The LNG IUS is similar in shape to the Copper T380 in that it also consists of a small T-shaped frame with a reservoir that contains LNG, a progesterone. The IUS releases 20 mcg of LNG per day into the uterine cavity for as long as 5 years. It consists of a polyethylene frame with a cylinder containing a polydimethylsiloxane-levonorgestrel mixture enveloping the vertical arm. The cylinder is coated with a membrane that regulates the release of the hormone. This model also is visible on x-ray.
An IUD causes cervical mucus to be thicker in consistency, thereby altering sperm migration. Uterotubal fluid and motility changes inhibit sperm migration. IUD also results in endometrial suppression.
Efficacy: The failure rate is 2% with the progesterone form, 0.6% with the Copper T380, and of 0.1 % with the LNG IUS. The percentage of women who continue to use these forms of contraception are high after 1 year of use, 81% and 78% with the progesterone forms and copper T380 respectively.
Advantages: IUDs produce no systemic side effects. Ectopic pregnancies are reduced overall; however, the ratio of extrauterine to intrauterine pregnancy is increased if conception does occur. Decreased menstrual blood loss occurs with progesterone IUD. Decreased dysmenorrhea occurs with progesterone IUD. Twenty percent of women experience amenorrhea with LNG IUS.
Disadvantages: Risk of uterine perforation at time of insertion exists. Increased dysmenorrhea occurs with Copper T380. Increased menstrual blood loss occurs in first few cycles with Copper T380 and LNG IUS. Controversy exists regarding whether IUD increases risk of PID. IUD has none of the potential noncontraceptive benefits of hormonal contraceptives. IUDs may be expelled unnoticed. IUDs do not protect against STDs.
Contraindications include history of previous PID, abnormal or distorted uterine cavity, undiagnosed genital bleeding, uterine or cervical malignancy, history of ectopic pregnancy, increase susceptibility to infection (leukemia, diabetes, valvular heart disease, AIDS), Wilson disease, known or suspected pregnancy, history of genital actinomyces, and active cervical or endometrial infections.
|
|
STERILIZATION | ¡@ |
Sterilization is considered an elective permanent method of contraception. Although both female and male sterilization procedures can be reversed surgically, the surgery is technically more difficult than the original procedure and may not be successful. Success is noted to be greater with tubal reanastomosis than with reanastomosis of the vas deferens in regards to reversal of sterilization.
Female sterilization
Approximately 1 million American women are sterilized either by surgery on the fallopian tube or hysterectomy each year. Sterilization can be performed in the postpartum period with a small transverse infraumbilical incision or during the interval period. Sterilization during the interval period can be performed with laparoscopy, laparotomy, or colpotomy. The methods of fallopian tube sterilization include occlusion with Falope rings, clips, bands, segmental destruction with electrocoagulation, or suture ligation with partial salpingectomy. Female sterilization prevents fertilization by interrupting the fallopian tube.
Efficacy: The United States Collaborative Review of Sterilization has examined the failure rate of female sterilization. Rates vary according to the procedure performed. The cumulative 10-year failure rate with each method of tubal ligation is as follows: spring clip method is 3.7%, bipolar coagulation is 2.5%, interval partial salpingectomy is 2%, silicone rubber bands is 2%, and postpartum salpingectomy is 0.8%.
Advantages: Female sterilization does not involve hormones. It is a permanent form of contraception. No data indicate that change in libido, menstrual cycle, or lactation occurs. Female sterilization usually is a same day procedure.
Disadvantages: Female sterilization is a procedure that involves general or regional anesthesia. It is permanent contraception, and patients may regret the decision later. Sterilization does not protect the patient from STDs. Sterilization involves all of the risks of surgery. It creates short-term discomfort.
Vasectomy
Vasectomy involves incision of the scrotal sac, transection of the vas deferens, and occlusion of both severed ends by suture ligation or fulguration. The procedure usually is performed under local anesthesia in an outpatient setting. Complications include hematoma formation and sperm granulomas. Occurrence of spontaneous resolution is rare. After sterilization, remnant sperm remains in the ejaculatory ducts. The man is not considered sterile until he has produced sperm-free ejaculates as documented by semen analysis. This usually requires 15-20 ejaculations. Vasectomy prevents the passage of sperm into seminal fluid by blocking the vas deferens.
Efficacy: The failure rate is determined to be approximately 0.1%.
Advantages: Vasectomy involves no hormones, it is permanent, it is an outpatient procedure, it is quick, and risk from the procedure is minimal.
Disadvantages: Patients may regret the decision later. Alternative contraception is required until the ejaculate is deemed sperm-free. Vasectomy does not prevent STDs. Short-term discomfort occurs.
|
|
EMERGENCY POSTCOITAL CONTRACEPTION | ¡@ |
Emergency postcoital contraception is defined as the use of a drug or device to prevent pregnancy after unprotected sexual intercourse. Unwanted pregnancy is common; worldwide about 50 million pregnancies are terminated each year. In the United States, each year, the widespread use of emergency contraception may have prevented over 1 million abortions and 2 million pregnancies that end in childbirth.
A variety of different methods of emergency contraception has been described. Emergency contraceptives available in the United States include the emergency contraceptive pills (ECP), the Copper T380 IUD, and the minipill emergency contraception method (MECM). Both the Preven kit and the Plan B kit are marketed as emergency contraceptives.
Candidates for emergency contraception include reproductive-aged women who have had unprotected sexual intercourse within 72 hours of presentation independent of the menstrual cycle. No known absolute contraindications to any of these methods exist because the high-dose of hormones is short lived. However, cases of deep vein thrombosis (DVT) in women using the ECP method have been documented.
Emergency contraceptive pills and the minipill emergency contraception method
The ECP mode utilizes 2 OCs, each containing 0.05 mg of ethinyl estradiol and 0.5 mg of norgestrel, ingested 12 hours apart for a total of 4 pills. The first dose should be taken within the first 72 hours after unprotected intercourse; however, studies do demonstrate effectiveness if taken after that period.
Only the progestin levonorgestrel has been studied for the use in MECM. The treatment schedule is 1 dose of 750 mcg levonorgestrel taken as soon as possible and no later than 48 hours after unprotected intercourse and a second dose taken 12 hours later.
The mechanism action of either the ECP or MECM is not clearly established. If administered before ovulation, both methods may inhibit follicular development and maturation, resulting in anovulation and deficient luteal function. Treatment following ovulation may affect the endometrium, thus inhibiting implantation. They also may affect tubal transport of the sperm or ova. However, both menses and fertility return with the next cycle.
Efficacy: Most studies cite an effectiveness rate of 55-94%, with the true effectiveness rate likely to be about 75%. Based on one randomized trial comparing the ECP protocol to the MECM, the MECM seems to be just as effective with far less nausea and emesis (Ho, 1993). Patients must understand that the effective rate of 75% does not translate into a 25% failure rate. Instead, when considering 100 women who have had unprotected sexual intercourse during the middle 2 weeks of their cycle, approximately 8 will become pregnant. Of those 8 who have used ECPs, only 2 will then become pregnant. Despite this significant reduction in the rate of pregnancy, patients must understand that this method of contraception should be used only in emergencies and that they should be encouraged to use other more consistent forms of contraception.
Several factors complicate the calculation of a failure rate. Factors include dependence on the patient's history of their last menstrual period and day of exposure, effect of regular and irregular menstrual cycles on the calculation of the estimated time of ovulation, the possibility of the patient being pregnant, and the possibility that more than one unprotected coitus has occurred during that period.
Disadvantages: Adverse effects include nausea and emesis, minor changes in menses, breast tenderness, fatigue, headache, abdominal pain, and dizziness. Ectopic pregnancy is possible if treatment fails.
Copper T380 intrauterine device
The Copper T380 IUD can be inserted as many as 7 days after unprotected sexual intercourse to prevent pregnancy. Insertion of the IUD is significantly more effective than either the ECP or MECP regimen, reducing the risk of pregnancy following unprotected intercourse by more than 99%.
|
|
FUTURE METHODS OF CONTRACEPTION | ¡@ |
In 1996, the Institute of Medicine (IOM) produced a report that examined the need for additional contraceptive choices and investigated the climate for development. The report was a follow-up to the 1990 IOM evaluation of obstacles and opportunities for contraceptive development. Their findings noted that the array of contraceptive choices was limited in regards to specific health problems, cultural differences, life cycle changes, and reproductive intentions. The committee also noted that regulatory issues, political pressures, and legal concerns have deterred pharmaceutical manufacturers from investigating new forms of contraception despite the evidence of need and market demand. As a result, the burden of research and development has shifted to small firms and nonprofit organizations that are not as well-equipped to bring new contraceptives to market.
Although contraceptive development in the United States has slowed in the past few years, research outside of the United States continues at a rapid pace. Many new contraceptive designs are under investigation to provide a greater variety of contraception that have fewer side effects, are safer, and are more efficacious. As a final note to this chapter, a few of the newer methods and forms of contraception soon to be on the market will be discussed.
Soon to be available in the United States is a contraceptive transdermal patch that releases estrogen and progesterone directly into the skin (Evra). Each patch contains a 1-week supply of hormones. It releases a sustained low daily dose of steroid doses equivalent to the lowest-dose oral contraceptive. Advantages include greater compliance and decreased adverse effects, such as nausea and vomiting, due to avoidance of the first pass effect. However, the patch may cause skin irritation, and, if it is removed unnoticed, such as from showering, it may compromise efficacy.
One of the more exciting new developments is a hormonal contraceptive method for men. The male birth control pill manipulates steroid hormones to decrease spermatogenesis, as well as testosterone secretion.
Newer methods of subdermal implants are on the horizon. Implanon is a single-rod implant that is 4 cm long and 2 mm in diameter. It consists of 68 mg of etonogestrel in an ethylene vinyl acetate copolymer core. Etonogestrel is a biologically active metabolite of desogestrel. Desogestrel is significantly more potent than levonorgestrel; a serum concentration of 0.09 ng/mL can inhibit ovulation in most women. Serum concentrations are adequate for contraception coverage for approximately 3 years. In more than 10 different studies utilizing 4000 women-years of use, no pregnancies have been demonstrated.
The advantages it has as compared to the Norplant system include higher incidence of amenorrhea and oligomenorrhea, decrease in the incidence of frequent and prolonged bleeding, and a decrease in the incidence of side effects such as weight gain, headache, and acne. When the rod is removed, the return to fertility is rapid, with return of ovulation within 3 weeks. Implanon was approved for usage in the United Kingdom in 1999, it still awaits FDA approval in the United States. Understanding of the long-term effects and overall safety data are limited at this point.
Uniplant is also a single-rod implant system that consists of 55 mg of nomegestrol acetate in a capsule that is 3.5 cm long and 2.4 mm in diameter. Uniplant has been shown to be highly effective for as long as 1 year, with incidence and degree of menstrual irregularities similar to those of Norplant.
Clinical studies are in progress for a biodegradable implant, Capnor, to eliminate the necessity of implant removal. This is a single 40-mm rod that contains levonorgestrel and maintains contraceptive protection for 1 year.
Biodegradable pellet implants containing norethindrone and cholesterol currently are undergoing investigation. They dissolve within 2 years and release the norethindrone for 12-18 months. Insertion of the pellets has been demonstrated to be simple; however, if the patient wishes for removal several months later, removal has been noted to be difficult.
The contraceptive vaginal ring is a new form of contraception that is expected to be on the market in the near future. The actual design of vaginal rings as a mode of contraception was first developed in the 1970s. The first rings studied were homogenous devices with the steroid mixed uniformly through a polysiloxane matrix. The design was abandoned because of a high initial release of drug with rapid decrease of drug release thereafter. The vaginal rings can deliver progesterone or progesterone/estrogen combinations. The combined ring is in the most advanced development phase. It releases both norethindrone acetate and ethinyl estradiol. The hormones are released slowly and absorbed directly by the reproductive organs. Preliminary studies demonstrate efficacy of prevention of pregnancy similar to OCs with fewer side effects. These would be used in the same schedule as OCs, with 3 weeks of ring usage and 1 week without to produce a withdrawal bleed.
The vaginal sponge, introduced in 1983 and taken off the market shortly after, is making a comeback. The contraceptive was deemed safe by the FDA. However, the plant it was manufactured in was not. American Home Product's plant had many problems, such as high levels of bacteria in its air and water, which were felt to be too costly to fix for a product that generated only 17 million dollars yearly in sales. Allendale Pharmaceutical has now bought the patent and equipment and has moved production to a new plant. Allendale Pharmaceutical currently is in the process of sponge production and marketing; however, the company is still awaiting FDA inspection of the plant for adherence to health regulations before it can return the vaginal sponge to the market.
The vaginal sponge is made of soft disposable polyurethane foam that contains the spermicide nonoxynol-9. It offers an immediate and continuous presence of spermicide throughout a 24-hour period. The polyurethane foam is designed to trap and absorb semen before the entry of sperm into the cervix. Clinical trials have demonstrated an efficacy rate of 89% and 91% for parous and nulliparous women respectively.
Lea's Shield is a 1-size-fits-all diaphragmlike device soon to be available in the United States. This device consists of a 1-way valve that allows air to escape during placement, thus creating a suction effect against the cervix. The unilateral direction of the valve permits uterine and cervical fluids to be released into the vaginal canal, but prevents sperm from entering. Currently, it is manufactured in Canada and Europe.
A few potential methods of tubal sterilization are under investigation. One of these new developments includes chemical scarring of the fallopian tubes. The scarring is a result of a combination of phenol and a thickening agent and phenol quinacrine that ultimately leads to blockage of the tubes. Another nonsurgical form of tubal sterilization is by utilizing chemical plugs. Approved for use in Canada, this entails introduction of methyl cyanoacrylate (Krazy Glue) into the fallopian tube. A reversible chemical plug also can be created by the injection of silicone into the fallopian tubes. The silicone eventually hardens but can be removed later. Chemical scarring and plugs are under investigation as potential methods of vasectomy as well.
A pregnancy vaccine is one of the most controversial and exciting forms of contraception under development. The pregnancy vaccine, unlike anti-infective vaccines, stimulates an immune response against one or more host-specific antigens. The targets of the immune response are accessible to the immune system during a finite time period, such as coitus (sperm antigens in the female), egg maturation (zona pellucida antigens), or successful fertilization (chorionic gonadotropin).
|
|
BIBLIOGRAPHY | ¡@ |