Contraception article:
Despite major advances in contraception that occurred during the 20th century, about 49% of pregnancies in the United States are unintended. More than half of these pregnancies end in abortion.
Despite major advances in contraception that occurred during the 20th century, about 49% of pregnancies in the United States are unintended. More than half of these pregnancies end in abortion.1
In 2000, 54% of women who obtained abortions had used a contraceptive method during the month they became pregnant; the most common methods were male condoms (28%) and oral contraceptives (OCs) (14%). Most of the unintended pregnancies resulted from incorrect or inconsistent use of contraceptives.2Among the remaining 46% of women who had an abortion in 2000, the reasons they gave for not using birth control included concerns about contraceptive methods (32%) and unexpected intercourse (27%).2
Advances in contraceptive technology have resulted in improved compliance and fewer side effects. Here we describe recent developments in hormonal and nonhormonal methods. The Table provides a comparative summary of existing methods.
COMBINATION ESTROGEN/ PROGESTERONE METHODS
Oral contraceptives. These continue to be the most common method of birth control, accounting for about 25% of all contraceptive use.3 However, despite advances in combination hormonal pill formulations, compliance remains a major problem. Among OC users, 47% missed 1 or more pills per cycle and 22% missed 2 or more.4
Newer progestins. To minimize adverse effects, newer formulations of progesterone have been combined with the lowest effective dose of estradiol. One such progesterone is drospirenone, a spironolactone analog with antimineralocorticoid activity. When combined with 30 µg of estrogen in the OC Yasmin, drospirenone does not cause the small rise in blood pressure and weight gain sometimes seen with other combination pills.5Although no changes in potassium levels were seen in women taking Yasmin, the manufacturer suggests monitoring levels in those who use potassium-sparing medications.6
Reducing hormone-withdrawal effects. Extending the number of active pills in some monophasic pill regimens can reduce headache, dysmenorrhea, hypermenorrhea, and premenstrual syndrome (PMS) related to hormone withdrawal during the placebo week. Some women who take a standard 28-day OC regimen experience these symptoms monthly.7
Seasonale is the first extended-cycle OC that contains 84 days of active-hormone pills followed by 7 days of hormone-free pills. Breakthrough bleeding was the most common reason for discontinuation.8
Mircette is another combination pill designed to reduce withdrawal effects. Instead of the standard 7-day placebo, the Mircette regimen has only 2 days of hormone-free pills, followed by 5 days of 10-µg estrogen pills. This regimen can ameliorate headaches and PMS associated with hormone withdrawal as well as provide greater ovarian suppression.9
Vitamin supplementation. Combination OCs that contain iron have been available for years. An OC that contains 0.4 mg of folic acid is currently in development.10
The transdermal patch (Ortho Evra) releases 20 µg of ethinyl estradiol and 150 µg of progestin daily. One patch per week for 3 weeks is applied directly to the arm, buttock, or abdomen, followed by a patch-free interval of 7 days.
In a large randomized controlled trial, compliance was better with the patch than with OCs.11 In the patch group, the method failure rate and side effects were similar to those in the OC group, with the exception of application site reactions and a higher incidence of breast tenderness and spotting observed within the first few cycles.12 The overall failure rate of the patch in a large pooled study was 0.8%, although evidence suggests that the patch may be less effective in women who weigh more than 90 kg (198 lb).13
In November 2005, the manufacturer warned users that the patch exposes them to significantly higher doses of hormones and may put them at greater risk for blood clots and other serious side effects than was previously believed. In addition, the FDA approved updated labeling for the patch stating that users are exposed to about 60% more estrogen than those who take typical birth control pills, because hormones from the patch are eliminated from the body differently than those from OCs.
Vaginal contraception ring. This device (NuvaRing) is another unique method of delivering combination estradiol and progesterone. A flexible ring is inserted into the vagina and left in place for 3 weeks. It is then removed for a ring-free interval of 7 days before a new ring is inserted. The ring delivers 120 µg of progestin and 15 µg of estradiol per day and results in complete anovulation. It is associated with less breakthrough bleeding than other very low estrogen contraceptive methods.14 Unlike the patch and the pill, the ring can maintain cycle control with an estrogen dose lower than 20 µg.
The failure rate of the ring (0.65%) is comparable to that of other methods; however, it has not been widely studied. The most common side effect is vaginitis, followed by symptoms typically associated with OCs. The discontinuation rate is lower than is generally reported for OC users, and the compliance rate appears high, with correct use reported in 90.8% of cycles.15
Although patients are instructed to start using the ring or the patch after menses, either method can be initiated at any time with 7 days of backup contraception.10 In the first 7 days of using the ring or patch, patients should also use a condom with spermicide or another barrier method, or abstain from sex, since it may take a few days for the ring or patch to become active. Extended use of the ring, as well as the patch, is under study.10
Monthly injection contraceptive. Lunelle contains 25 mg of medroxy-progesterone acetate (the hormone in Depo-Provera) and 5 mg of estradiol. Although this injectable contraceptive has been available in other countries for more than 20 years and was released for marketing by the FDA in 2000, it is currently not marketed in the United States; whether it will be is unknown.16-18
The once-a-month injection is highly effective; the 1-year failure rate is between 0% and 0.2%.17 Unlike OCs, certain oral medications will not impair the effectiveness of Lunelle, because the injection circumvents hepatic first-pass metabolism.16 Bleeding irregularity may be more common in monthly injection users than in OC users; however, it is less frequent than that in progesterone-only contraception users.Other side ef-fects include weight gain, breast tenderness, and mood changes.16
PROGESTIN-ONLY METHODS
Progesterone-releasing intra-uterine device. Mirena releases 14 to 20 µg of levonorgestrel per day and causes thickening of cervical mucus, impairment of sperm migration, and alteration of the endometrium. Unlike the copper intrauterine device (IUD), Mirena also has an anovulatory effect (5% to 15% of cycles).
The most commonly reported adverse effect is amenorrhea (occurs in 20% of cycles after 1 year of use). Mirena is used off-label for this "side effect" in menorrhagic women, with a 90% reduction in mean menstrual blood loss.19 Irregular breakthrough bleeding occurs frequently in the first few cycles and is the most common reason for discontinuation.20
Mirena is as effective as certain forms of sterilization; the failure rate is 0.1% (the cumulative failure rate over 5 years is 0.7%).21 Mirena, like other IUDs, is contraindicated in women at risk for pelvic inflammatory disease and may be expelled more easily in nulliparous women.
Progesterone implant. Implanon--a single-rod implant placed under the skin in the upper arm--releases 60 µg of progestin a day for 3 years. The effectiveness is similar to that of Norplant; no pregnancies have been reported in preliminary studies. Insertion and removal are easier with the single rod. Bleeding patterns are similar to those observed with Mirena. The implant is available in Europe and is expected to be marketed in the United States within a year.10
Other methods. Other progesterone implantable devices, as well as a progesterone-releasing ring, are expected to become available in the United States. These devices may be appropriate for breast-feeding women or in women in whom estrogen use is contraindicated.10
NONHORMONAL METHODS
Many women are not candidates for hormonal contraceptive methods because of side effects, contraindications, or patient preference. More than 60% of women stated that their ideal form of contraception would be nonhormonal.3
Barrier methods. An added benefit ofbarrier methods is that they can reduce the risk of sexually transmitted infections. The polyurethane Reality female condom, when used with a polyurethane male condom, is an acceptable contraceptive method in women with allergies to latex. However, the typical failure rate is relatively high (21% per year), and the condom is somewhat difficult to use.10 Lea's Shield--a reusable silicone vaginal contraceptive that forms a seal over the cervix--when used with spermicide has a 1-year failure rate of 9% (14% without spermicide); however, preliminary studies of this method have been small.22 A polyurethane sponge impregnated with nonoxynol-9 (the Today sponge)--a popular over-the-counter contraceptive from 1983 to 1995 that became unavailable because of manufacturing problems--is now on the market again.
Fertility awareness. Natural methods of family planning are hardly considered breakthroughs in technology, and their effectiveness remains largely unknown. Nevertheless, about 2 million women in the United States use a form of natural family planning as their primary method, and an even greater number of women combine some form of rhythm method with barrier use.23
Worldwide, an estimated 3% of women rely solely on fertility awareness. Fostering fertility awareness involves teaching a woman to identify the fertile period in her cycle, at which time she can either abstain from sex or use backup contraception. Traditionally, women have identified their fertile period by marking the days on a calendar, monitoring their temperature, or checking cervical mucus. Newer methods include fertility monitors and the use of color-coded beads to keep track of fertile days.24 Studies to determine whether combining newer methods will increase effectiveness are under way; however, the results of a recent Cochrane review were inconclusive, largely because of high discontinuation rates.25
EMERGENCY CONTRACEPTION
Two forms of emergency contraception have been approved for this indication by the FDA. The American College of Obstetricians and Gynecologists recommends that Plan B be used preferentially because of the lower failure rate and fewer side effects.26
Plan B consists of 2 tablets, each with 0.75 mg of levonorgestrel, that can be taken in 1 dose after contraceptive failure or after unprotected intercourse.27 (Note that taking the 2 tablets together is an off-label use.) The precise mechanism of Plan B is unknown. Emergency contraception may inhibit ovulation, thicken cervical mucus, affect endometrial maturation, and interfere with sperm transport.9,28 Although emergency contraception is not thought to disturb an implanted pregnancy, its likely mechanism of preventing a fertilized ovum from implanting can make Plan B an unacceptable choice for some patients and practitioners.27
Plan B reduces the pregnancy rate by 89%. The effectiveness is inversely proportional to the time since intercourse; consequently, it is most effective when started within 24 to 72 hours.27 Therefore, consider providing an advance prescription for Plan B during contraceptive counseling (Box).
References:
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