A high proportion of all American women who are at risk of unintended pregnancy use reversible methods of contraception (57%) and the majority of women currently using reversible methods use the pill or the condom (76%).o
Our new national estimates show that about one in every eight uses of a reversible method results in a contraceptive failure during the first year. This estimate reflects typical use, including incorrect and inconsistent use. Between 1995 and 2002, the probability of contraceptive failure during use of all reversible methods combined declined by almost 20%—from 14.9% to 12.4%—although the change is not statistically significant. Increased proportions using two of the more effective methods (injectables and the pill), and a lower proportion using the condom alone (which has much lower effectiveness than the two hormonal methods) account for part of this overall improvement in contraceptive effectiveness.
Our estimates show a high probability of failure for fertility-awareness-based methods (25%), and an intermediate risk for the male condom and withdrawal (17% and 18%, respectively). Two hormonal methods, injectables and the pill, (with probabilities of failure of 7% and 9%, respectively) are by far the most effective reversible methods being used by a sizable number of U.S. women.p
The effect of the correction for abortion varies for estimates of the individual methods. This variation could be a reflection of differences in the propensity to report abortions among users of the various methods in the NSFG or a differential tendency to report method use at the time of conception in the two surveys. Inclusion of unreported abortions has very little effect on the estimate of failure for withdrawal, leads to a slightly lower estimate for injectables and a slightly higher estimate for the pill. But the correction increases the estimate for fertility-awareness-based methods and leads to a much higher estimate for condoms. The effect of the correction implies that more abortions are reported during use of fertility-awareness-based methods and the condom in the APS than in the NSFG.
Changes in the characteristics of users of specific methods may help to explain changes in the probability of contraceptive failure between 1995 and 2002. For example, socioeconomic groups with traditionally higher risks of failure may make up a greater proportion of users of certain methods in 2002 compared to 1995, and thereby account for a rise in estimates of the probability of contraceptive failure. An increase in the first year probability of failure for the injectable contraceptive occurred between 1995 and 2002 (from 5.4% to 6.7%), and while this increase was not statistically significant, it may be due in part to a shift in the composition of the population of women using it. In fact, increases in the proportion of women using injectables between 1995 and 2002 were greatest among Hispanic and non-Hispanic black women; q
we found that black women do face an elevated risk of failure relative to non-Hispanic white and other users of contraception when considering all methods combined. However, we did not have a sufficient number of observations to examine whether this difference holds among users of injectables only.
An increase was identified in the risk of failure among users of fertility-awareness-based methods (although not statistically significant): the already very high risk of failure among users of this group of methods in 1995 (22.6%) rose to 25.3% by 2002. On the other hand, the estimate of failure for withdrawal appears to have dropped dramatically — from 28.4% in 1995 to 18.4% in 2002 — but the wide confidence intervals surrounding these estimates (a result of the small size of the group using this method) mean that this decrease is not statistically significant. Estimates of the risk of failure for the pill (8.8% in 1995 and 8.7% in 2002) and the condom (17.8% in 1995 and 17.4% in 2002), the two most widely used reversible contraceptive methods, remained relatively constant from 1995 to 2002.
In 2002, women younger than 30, black women, those who intend a birth in the future, those who already have a birth, those who are poor or near poor, and women in a cohabiting union had a higher risk of failure compared to the relevant reference groups. Examining trends in contraceptive failure among subgroups of women, we found only that those who had never given birth were significantly less likely to become pregnant while using a method in 2002 than in 1995.
The socioeconomic factors associated with differential risks of failure are not the same for all methods. Women living in poverty who rely on a partner-dependent method — the condom or withdrawal — are nearly twice as likely to experience a failure as other women, but those in poverty who use the pill experience the same risk as higher income women who use that method. And while black women who use the condom are more likely to experience a failure than are women from other race/ethnic groups, race/ethnicity has no effect on the risk of failure for the pill or withdrawal.
A woman’s relationship with her partner also has differing effects on her risk of failure depending on her contraceptive method. For the pill, formal marriage is associated with the lowest risk of failure, with both those who are not in union and cohabiting women experiencing a higher relative risk. For the condom, however, only cohabiting women face an elevated risk of failure; women who are not in union are no more or less likely to experience a condom failure than married women. And for withdrawal, the critical distinction is between women who have ever been married and those who have not, with the latter experiencing a greater risk of failure. These method-specific differences likely represent the way in which effectiveness in using a method can be affected by the woman’s relationship with her sexual partner or partners as well as frequency of intercourse. Pill users who are not in a union may have less frequent intercourse than married pill users, but they may also be more likely to miss pills and delay refills. Similarly, we may see no difference in the risk of failure between single and married condom users if the coital frequency of the former is much less. And for users of the withdrawal method — which is very much a partner dependent method — the woman’s risk of failure may be strongly influenced by the degree to which she and her partner have discussed their childbearing intentions, a discussion that is far more likely to have occurred among ever married couples than those who have never been married.
These analyses also indicate that some factors identified as affecting the risk of failure among users of any reversible method have similar effects on the risk of failure among users of the three specific methods that could be examined (pill, condom and withdrawal): the woman’s age, her intention toward a future birth, and whether she has already had a birth. These individual method analyses support the conclusion that, for users of all three of these methods and probably for users of every reversible method, women age 30 and older enjoy a much lower risk of failure than younger women, as do contraceptive users who intend no more births and those who have never had a birth.
Findings from other research suggest that the relatively high probabilities of contraceptive failure measured in the current study are plausible. A national study of patterns of contraceptive use among women at risk of unintended pregnancy found that 24% switch methods during a one-year period, increasing the risk of failure given adjustment to use of a new method [17
]. Another study demonstrated the positive relationship between strength of motivation to prevent an unintended pregnancy, and using contraception continuously [18
]. A similar positive relationship is found between motivation to prevent unintended pregnancy and greater consistency in using methods (Jennifer Frost, personal communication, May 2007). These findings provide support for the differentials in risk of failure that we found for union status and intentions regarding future births.
In 2002, more than 98% of U.S. women 15–44 years of age who had ever had sexual intercourse with a male had used at least one contraceptive method [16
]. Ninety percent of all women ages 15–44 had ever had a partner who used the condom and 82% had ever used the pill [16
]. Thus, most American women are experienced at trying to avoid unintended pregnancy. However, while the rate of unintended pregnancy has remained unchanged from 1995 to 2002, there has been a small decline in the proportion of unintended pregnancies that occurred during use of contraception (51% in 1994 v. 48% in 2001) [1
], and overall use of contraception among women at risk of unintended pregnancy has also dropped, from 92.5% in 1995 to 89.3% in 2002.r
Both of these trends may indicate an increased tendency among women to rely on chance rather than contraception, particularly among those subgroups most vulnerable to the risk of failure. In fact, the proportion using contraception among women in poverty at risk of pregnancy dropped from 92.1% in 1995 to 86.3% in 2002.s
Barriers to effective contraceptive use include partner opposition, difficulty in obtaining a method, and difficulty in use. But even among women who overcome those hurdles and do use a method, the effectiveness of a method greatly depends on vigilance and effective use by the woman and her partner. The substantial differences in probabilities of failure among socioeconomic subgroups in the United States indicates that many of these difficulties are not being overcome, and they may have become even harder to overcome in recent years for some socially and economically disadvantaged groups of women than for other women. The extent to which relatively high probabilities of failure may lead to discouragement among users and lessened use is not yet known. But high risks of failure could make it more difficult to convince nonusers to adopt contraception and to convince those already using to continue.
Particular attention should be paid to reducing barriers to contraceptive access for disadvantaged groups of women. In addition, there is much room to improve effectiveness of condom use given the large gap between the probabilities of failure during typical and perfect use. The Healthy People 2010 goal of reducing the overall probability of contraceptive failure from 13% in 1995 to 7% by 2010, as well as reducing failure among specific disadvantaged population groups, will be very difficult in the absence of major policy and programmatic interventions. A number of strategies need to be pursued simultaneously if this goal is to be reached: increased education and provision of information to reduce misperceptions about methods; improved access to contraceptive services including a wide choice of methods including long-acting methods such as injectables, implants and IUDs; and more widespread practice of counseling for both women and men to improve consistency and correctness of use, as well as to improve communication between partners about contraceptive use and planning pregnancies.