|
Closing the Effectiveness Gap |
|
| June 2007 Issue No. 13 |
The INFO Project • Johns Hopkins Bloomberg School of Public Health • Center for Communication Programs • 111 Market Place, Suite 310 • Baltimore, Maryland 21202, USA • 410-659-6300 • 410-659-6266 (fax) • www.infoforhealth.org • infoproject@jhuccp.org | |
ACHIEVING CONTRACEPTIVE EFFECTIVENESS
For most people, the most important reason given for choosing a particular contraceptive method is how well it protects against pregnancy (48, 100, 106, 111, 112, 132). Many contraceptive users, however, do not achieve the protection from pregnancy that they want.
|
The World Health Organization (WHO) has estimated that, worldwide, nearly one-third of unintended pregnancies—an estimated 26.5 million in 1993 (the most recent data available)—result from either incorrect or inconsistent contraceptive use or from method failures (that is, because the contraceptive itself did not work properly) (138). Most unintended pregnancies among contraceptive users occur because of errors in use rather than method failure (25, 41).
An estimated 40% to 60% of total unintended pregnancies are due to incorrect or inconsistent method use, while method failure is estimated to account for less than 10%. Unintended pregnancies among women not using any contraceptive method account for the remainder (28, 63, 77).
Choosing a long-acting method that requires little or no user action, such as intrauterine devices (IUDs), contraceptive implants, or sterilization, is the best way to ensure high contraceptive effectiveness. Still, if these methods are not suitable to clients, other methods that require user action can provide effective contraceptive protection—including oral contraceptives, barrier methods, and fertility awareness methods.
For most methods that require user action, generally the most effective method for any individual is the one that the person uses correctly and consistently (88, 110, 119). For these methods, contraceptive effectiveness depends not only on the method’s inherent effectiveness—that is, its biological ability to protect against pregnancy when used correctly and consistently—but also on the extent to which the user follows the method’s rules for correct and consistent use (110, 118, 119). Following the method’s rules for correct and consistent use will enable many clients to close the gap between the effectiveness of the method as typically used and its inherent effectiveness.
Perfect Use and Typical Use
Two standard measures of contraceptive effectiveness—“perfect-use” and “typical-use” pregnancy rates—have been developed to distinguish between unintended pregnancies due to method failure and those due to contraceptive use errors.1 Perfect-use pregnancy rates provide the best measurement of the effectiveness of contraceptive methods when used correctly and consistently; these rates point to the probabilities of pregnancy due to the method itself failing and provide the best measurement of a method’s inherent protection (118).
Typical-use pregnancy rates represent contraceptive effectiveness as the average person uses the methods (119). Typical-use rates include pregnancies that occur among both users who make mistakes and users who always use the method and always use it correctly. An individual user could achieve much more or much less contraceptive protection than the typical-use rate indicates, depending on the extent to which she or he is able to achieve correct and consistent use.
|
Perfect-use pregnancy rates are obtained from clinical trials of contraceptive effectiveness and safety. In clinical trials participants closely monitor their contraceptive use to identify and report monthly cycles when they used the method correctly and consistently. Perfect-use pregnancy rates reflect the number of women using the method correctly and consistently who become pregnant (110).
Typical-use pregnancy rates reflect the total number of women using the method who become pregnant (including both people using the method correctly and consistently and users who make mistakes) (110). Typical-use rates generally are obtained from nationally representative surveys of contraceptive users (41, 119). Participants in such surveys are more likely than those in clinical trials to represent typical users under typical conditions.
For long-acting contraceptive methods that require little or no action on the part of the user, typical-use pregnancy rates are either exactly the same or nearly the same as perfect-use pregnancy rates. For other methods that require more user action, however, typical-use pregnancy rates are measurably higher than perfect-use rates, and often substantially higher (see “Effectiveness gap differs by method” and Table 1).
Perfect-use and typical-use pregnancy rates usually are measured in the first year of contraceptive use. Pregnancy rates over several years of use generally are available only for long-acting methods, such as IUDs, implants, and sterilization, because enough people use these methods for longer than one year to permit measurement. Long-term pregnancy rates are difficult to compare among contraceptive methods because the time periods measured vary according to the effective life span of the method under study (105, 127). (For long-term pregnancy rates of IUDs, implants, female sterilization, and vasectomy, see the publication, Family Planning: A Global Handbook for Providers (136).)
First-year pregnancy rates provide a good indication of the risk of pregnancy with contraceptive use, whether in perfect use or in typical use. In general, pregnancy rates are highest in the first year of use, because contraceptive users who are most likely to become pregnant do so within a year of use. Also, some methods are more likely to fail in the first year of use than later. Nonetheless, pregnancy rates with contraceptive use continue to increase over each year of use, and family planning clients should be aware of this important fact (see “Explain Long-Term Effectiveness”).
Table 1. Contraceptive Effectiveness |
|||||||||||||||||||
|
Number of Unintended Pregnancies Per 100 Women During the First Year of Contraceptive Use |
|||||||||||||||||||
|
|
Number of Unintended Pregnancies Per 100 Women |
|
|||||||||||||||||
|
Contraceptive Method |
During Typical Usea |
During Correct and Consistent Usea |
|||||||||||||||||
|
Implants |
0.05 |
0.05 |
|||||||||||||||||
|
Vasectomy |
0.15 |
0.1 |
|||||||||||||||||
|
Levonorgestrel-releasing IUD |
0.2 |
0.2 |
|||||||||||||||||
|
Female sterilization |
0.5 |
0.5 |
|||||||||||||||||
|
Copper-bearing IUD (TCu-380A) |
0.8 |
0.6 |
|||||||||||||||||
|
Lactational amenorrhea method (LAM) (for 6 months only) |
2 |
0.9 |
|||||||||||||||||
|
Combined monthly injectables |
3 |
0.05 |
|||||||||||||||||
|
Progestin-only injectables |
3 |
0.3 |
|||||||||||||||||
|
Combined oral contraceptives |
8 |
0.3 |
|||||||||||||||||
|
Progestin-only oral pills |
8 |
0.3 |
|||||||||||||||||
|
Combined patch |
8 |
0.3 |
|||||||||||||||||
|
Combined vaginal ring |
8 |
0.3 |
|||||||||||||||||
|
Male condom (without spermicide) |
15 |
2 |
|||||||||||||||||
|
Diaphragm with spermicide |
16 |
6 |
|||||||||||||||||
|
Female condom (without spermicide) |
21 |
5 |
|||||||||||||||||
|
Fertility awareness methods |
25 |
b |
|||||||||||||||||
|
Ovulation method |
c |
3 |
|||||||||||||||||
|
TwoDay Method® |
c |
4 |
|||||||||||||||||
|
Standard Days Method® |
c |
5 |
|||||||||||||||||
|
Withdrawal |
27 |
4 |
|||||||||||||||||
|
Spermicides |
29 |
18 |
|||||||||||||||||
|
Cervical cap |
32d, 16e |
26d, 9e |
|||||||||||||||||
|
Based on Appendix A in World Health Organization and Johns Hopkins Bloomberg School of Public Health 2007 (136). a First-year contraceptive pregnancy rates largely from the United States. Source: Trussell 2007 (120). Rates for monthly injectables and cervical cap are from Trussell 2004 (118). Six-month rate for LAM during correct and consistent use is the weighted average from Kazi 1995 (64), Labbok 1997 (69), Pérez 1992 (84), and Ramos 1996 (92); during typical use from Kennedy 1996 (65). |
Effectiveness gap differs by method. The gap between perfect-use and typical-use pregnancy rates depends both on a method’s inherent protection and on how difficult the method is to use perfectly. Methods have been grouped into three categories based on differences between perfect-use and typical-use pregnancy rates (108, 118):
-
Methods that are inherently highly protective against pregnancy and are nearly impossible to use imperfectly. Long-acting contraceptive methods—female sterilization, IUDs, and implants—fall into this category. Once the procedure is done, little or nothing is required of users to assure effectiveness. In other words, there are no mistakes for the user to make. Therefore typical-use and perfect-use pregnancy rates, as shown in Table 1, are almost the same. Vasectomy is also a long-acting and highly effective method that requires little of the user, except to use a backup method for three months after the vasectomy procedure, until the method takes effect (141).
-
Methods for which proper use plays an important role in contraceptive effectiveness. Oral contraceptives have low pregnancy rates if women use them correctly and consistently. Typical-use pregnancy rates are substantially higher than perfect-use rates, however. These are clear signs that following the method’s rules for correct and consistent use largely determines effectiveness of oral contraceptives (122). Injectable contraceptives fall between these first two categories. That is, users of injectables need only to remember to have repeat injections—either monthly for combined injectables or every three months for progestin-only injectables—to ensure contraceptive effectiveness.
-
Methods that have a wide range of typical-use pregnancy rates among different studies and groups of users. Barrier methods, fertility awareness methods, spermicides, and withdrawal are in this category. Perfect-use pregnancy rates are substantially lower than typical-use rates, illustrating that proper use of these methods plays an important role in their effectiveness. The difference between this category and the category above is that typical-use pregnancy rates vary widely from one study to another and from one group of users to another (for example, see Figure 1, below). For these methods, the large variations in effectiveness suggest that personal characteristics, user behavior, and programmatic factors often are more important than the inherent effectiveness of these contraceptives in determining probability of pregnancy (41, 50, 81, 88, 110, 120).
Figure 1. Condom Effectiveness Varies by Country12-Month Typical-Use Pregnancy Rates Among Married Women Relying on Condoms, Selected Countries  |
Closing the Effectiveness Gap
To achieve the best possible contraceptive protection against unintended pregnancy, family planning clients must make an informed decision to choose, from among available methods suitable to their individual circumstances, the one that combines the greatest inherent effectiveness with their own ability to use it correctly and consistently. Many people, however, have poor knowledge about contraceptive effectiveness—including people who have discussed family planning with a health care provider (32, 111, 112).
|
Family planning programs can help close the gap. While contraceptive effectiveness depends primarily on the method and the user, programs can help clients ensure maximum protection against unintended pregnancy by keeping a range of methods continuously in stock so that clients can choose the method they prefer, by offering convenient ways to obtain methods so that clients do not interrupt use because their method is unavailable, and by ensuring that providers counsel clients about common side effects with the methods that their clients are considering—a problem that often interferes with correct and consistent contraceptive use (see, “How Programs Can Improve Contraceptive Effectiveness”).
For a client to use a contraceptive method well, the characteristics of the method must fit the individual’s circumstances (119). A person’s life stage, social and economic status, religious and cultural beliefs, reproductive intentions, family responsibilities, and work schedule all contribute to the initial choice of a family planning method and affect its continued use (7, 41, 56, 88, 119, 122). The characteristics of contraceptives themselves also influence a client’s preference for a specific method and affect how well the client can use the method. Side effects are the contraceptive characteristic that most commonly affect people’s preferences and proper use. Other characteristics include whether or not the method interferes with sex, how often a user has to take action to use it correctly, and the need for a partner’s cooperation to ensure effectiveness (119).
Ideally, counseling should be able to improve people’s ability to use family planning effectively. Successful counseling approaches to improve contraceptive use are difficult to define, however. The few studies that have addressed this issue have limitations, including small sample sizes, short follow-up periods, high loss of participants to follow-up, and varying counseling approaches that limit comparisons and conclusions (53, 80, 103).
Still, family planning providers can help clients make informed choices about effective contraceptive use. They can apply evidence on communicating risk information to explain contraceptive effectiveness in ways that clients are able to understand and can apply to the task of choosing a suitable method (see “How to Explain Contraceptive Effectiveness”). Also, they can counsel clients to use their chosen methods correctly and consistently, so that their clients can achieve the greatest effectiveness possible with their chosen method (see “Counseling for Effective Use”).
1 In epidemiological studies, the inherent protection of a contraceptive method—that is, how well the method works when used perfectly—is referred to as its “efficacy,” and how effective a method is in typical use, which includes incorrect and inconsistent use, is referred to as its “effectiveness” (72, 128). To distinguish between effectiveness when a method is used perfectly and as typically used, this report uses the terms “inherent effectiveness,” “greatest effectiveness,” and “effectiveness when used correctly and consistently” to refer to perfect-use conditions, and uses “effectiveness as typically used” to refer to typical-use conditions.
 |
 |
Information & Knowledge for Optimal Health (INFO) Project
111 Market Place Suite 310, Baltimore, MD 21202
Phone: 410-659-6300 Fax: 410-659-6266 Security & Privacy Policy