Objective
The purpose of this study was to determine women’s knowledge of contraceptive effectiveness.
Study Design
We performed a cross-sectional analysis of a contraceptive knowledge questionnaire that had been completed by 4144 women who were enrolled in the Contraceptive CHOICE Project before they received comprehensive contraceptive counseling and chose their method. For each contraceptive method, women were asked “what percentage would get pregnant in a year: <1%, 1-5%, 6-10%, >10%, don’t know.”
Results
Overall, 86% of subjects knew that the annual risk of pregnancy is >10% if no contraception is used. More than 45% of women overestimate the effectiveness of depo-medroxyprogesterone acetate, pills, the patch, the ring, and condoms. After adjustment for age, education, and contraceptive history, the data showed that women who chose the intrauterine device (adjusted relative risk, 6.9; 95% confidence interval, 5.6–8.5) or implant (adjusted relative risk, 5.9; 95% confidence interval, 4.7–7.3) were significantly more likely to identify the effectiveness of their method accurately compared with women who chose either the pill, patch, or ring.
Conclusion
This cohort demonstrated significant knowledge gaps regarding contraceptive effectiveness and over-estimated the effectiveness of pills, the patch, the ring, depo-medroxyprogesterone acetate, and condoms.
Many factors influence women’s decisions regarding contraceptive methods. Knowledge of a contraceptive method’s effectiveness can be an important factor in a woman’s choice of method. General contraceptive knowledge varies widely across populations, with notable disparities among minority and younger populations who have less awareness and understanding of various contraceptive methods. Multiple studies have evaluated women’s knowledge of a specific contraceptive method, such as the intrauterine device (IUD), or have evaluated the knowledge of women in countries outside the United States.
Among women who use reversible contraception, most choose less-effective methods such as condoms (26%) and oral contraceptive pills (45%). Reliance on less-effective methods contributes to the fact that nearly one-half of all pregnancies in the United States are unintended. Recently published data from the National Survey of Family Growth show an increase in the use of long-acting reversible contraceptives (LARC) that include IUDs and implants. LARC are not only the most effective methods but also appear to provide the highest satisfaction and rate of continuation among users.
Promoting the use of the most effective contraceptive methods requires an assessment of what women who desire reversible contraception know about the effectiveness of the available methods. The primary objective of this analysis was to determine the knowledge of contraceptive effectiveness among a cohort of women in St. Louis who were enrolled in the Contraceptive CHOICE Project (CHOICE). Our secondary objective was to assess whether women who chose LARC methods had better knowledge regarding the effectiveness of their own method before contraceptive counseling compared with women who chose the pill, patch, or ring.
Materials and Methods
CHOICE is a prospective cohort study that was developed to promote the use of LARC methods in the St. Louis region. The methods for CHOICE have been previously published, but a brief description is provided later. The CHOICE protocol was approved by the Washington University in St. Louis School of Medicine Human Research Protection Office before the initiation of recruitment.
CHOICE is a convenience sample of women in St. Louis City and County who desire reversible contraception. The primary objective of CHOICE is to promote the use of LARC and provide no-cost contraception to a large number of women in the St. Louis region in an effort to reduce unintended pregnancies. Participants are recruited from clinics that serve women at high risk for unintended pregnancy and sexually transmitted infections and from the local community through word-of-mouth. Recruitment occurs through general awareness about CHOICE through general and reproductive health clinics, referring healthcare providers, newspaper reports, and study flyers. Inclusion criteria for CHOICE include (1) aged 14-45 years, (2) a willingness to start a new reversible contraceptive method (may have used the chosen method previously but is not their current method of contraception), (3) no desire to conceive for at least 12 months, (4) being sexually active with a male partner (or an intent to be active in the next 6 months), (5) resides in or seeks clinical services at designated recruitment sites in the St. Louis region, and (6) the ability to consent in English or Spanish. Women were excluded if they had had a hysterectomy or sterilization procedure.
All potential CHOICE participants are read a short standardized script regarding LARC methods at the time of eligibility screening, regardless of whether they enroll in the project. This script states “one of [the] objectives [of the study] is to be sure women are aware of all contraceptive options, especially the most effective, reversible, long-acting methods. These methods include intrauterine contraception and the subdermal implant.” Women who choose to participate may then enroll the day that they hear the script or ≤30 days later; they will be rescreened for eligibility if >30 days have passed. All enrolled participants complete a written contraceptive knowledge questionnaire before receiving comprehensive contraceptive counseling and selecting their contraceptive method. All reversible contraceptive methods are presented during contraceptive counseling; contraceptive method effectiveness, common side-effects, risks, and benefits are described so that participants can make an informed decision.
The contraceptive knowledge questionnaire asks participants to indicate the typical-use failure rate of each contraceptive method. They are given a written questionnaire that stated: “We would like to get your best guess about how successful you think birth control methods are at preventing pregnancy. For each method of birth control, please tell us how many women you think would get pregnant in a year while using this method. What percentage (or number of women out of 100) do you think would get pregnant in a year using each method below?” The response categories are <1%, 1-5%, 6-10%, >10%, and don’t know. Participants are asked the effectiveness of the IUD, implant, depo-medroxyprogesterone acetate (DMPA), oral contraceptive pills, contraceptive patch, vaginal contraceptive ring, condoms, natural family planning, sterilization, and using “nothing” for contraception. Typical-use failure rates were used to define the correct answers and were categorized as “correct,” “overestimate,” “underestimate,” and “don’t know” ( Table 1 ).
| Contraceptive method | Women who experienced an unintended pregnancy (contraceptive failure) within the first year of typical use, % |
|---|---|
| No method (nothing) | 85 |
| Spermicides | 28 |
| Natural family planning | 24 |
| Condom (male and female) | 18–21 |
| Diaphragm | 12 |
| Combined and progestin-only pills | 9 |
| Contraceptive patch | 9 |
| Vaginal contraceptive ring | 9 |
| Depo-medroxyprogesterone acetate | 6 |
| Intrauterine device | 0.2–0.8 |
| Implantation | 0.5 |
| Sterilization (male and female) | 0.15–0.5 |
All women who enrolled in CHOICE from the study launch in August 2007 through December 2009 were eligible to be included in this analysis. Demographic and reproductive characteristics of the study participants are obtained with a staff-administered questionnaire during the enrollment session and are described with frequencies, percentages, means, and standard deviations for appropriate data type. Baseline covariates among different contraceptive method users were compared with the use of the chi-square test for categoric variables and analysis of variance for continuous normally distributed variables. Normality was assessed by evaluation of the histogram of continuous variables. Participants’ responses were evaluated for the entire cohort. Subsequently, we then conducted an analysis by chosen contraceptive method. We then assessed the likelihood of correctly estimating the effectiveness of the chosen method with univariate analysis with the χ 2 test. We evaluated the association of a participant’s reported contraceptive history on her knowledge of contraceptive effectiveness. We assessed the likelihood of correctly estimating the effectiveness of the chosen method with multivariable Poisson regression with robust error variance that was adjusted for age, education, and previous method use. We also performed the analyses of contraceptive effectiveness knowledge by chosen baseline contraceptive method. Because the published failure rates for the combination hormonal contraceptive patch and vaginal ring are the same as oral contraceptive pills, we chose to group users of these methods together as pill/patch/ring users. Additionally, because users of pill/patch/ring represent the largest proportion of women who use reversible contraception in the United States, they served as the referent group for this multivariable regression analysis.
Results
Of the 8413 women who were screened for eligibility, 5090 participants were eligible and enrolled in CHOICE between August 2007 and December 2009 ( Figure 1 ). Of the women enrolled, 4144 (81%) completed the baseline contraceptive knowledge tool before contraceptive counseling. The time from screening to enrollment and completion of the knowledge tool was distributed relatively equally between same day, within 1-14 days, 15-30 days, and >30 days. Overall, 71% of participants chose LARC; 47% of participants chose the levonorgestrel IUD; 11% of the participants chose the copper IUD, and 13% of the participants chose the contraceptive implant. Oral contraceptive pills (either combination or progestin-only) were chosen by 10% of the women; 8% of the women chose DMPA; 9% of the women chose the vaginal ring, and 2% of the women chose the contraceptive patch. We observed statistically significant differences in most of the demographic and baseline characteristics of the participants when they were grouped by chosen baseline contraceptive method ( Table 2 ). Overall, the mean age of participants at the time of enrollment was 25.2 ± 5.8 (SD) years. Participants who chose the copper IUD tended to be older and more educated compared with those participants who chose other methods, whereas users of the implant were younger and less likely to have attended or completed college. More than one-half of the participants reported difficulty paying for necessities or receiving government support; only 41% of the women reported that they had private health insurance. The majority of participants (59%) reported that they wanted ≤2 children.
| Variable | All users (n = 4144) a | Levonorgestrel–intrauterine device (n = 1958) | Copper intrauterine device (n = 447) | Implant (n = 541) | Depo-medroxyprogesterone acetate (n = 316) | Pill/patch/ring (n = 880) |
|---|---|---|---|---|---|---|
| Age at enrollment,y b , c | 25.2 ± 5.8 | 25.8 ± 5.7 | 28.1 ± 6.2 | 23.0 ± 5.9 | 24.5 ± 5.9 | 24.0 ± 4.8 |
| Age first had sex, y b , c | 16.3 ± 2.5 | 16.2 ± 2.4 | 16.3 ± 3.1 | 15.7 ± 2.2 | 15.9 ± 2.1 | 16.8 ± 2.5 |
| Education, % c | ||||||
| Less than high school/high school | 37.3 | 35.5 | 29.8 | 57.3 | 52.4 | 27.7 |
| Some college | 41.6 | 43.6 | 41.2 | 32.2 | 38.1 | 44.7 |
| College/graduate degree | 21.0 | 21.0 | 29.1 | 10.5 | 9.5 | 27.6 |
| Hispanic ethnicity, % c | 5.0 | 4.2 | 7.4 | 8.0 | 2.2 | 4.7 |
| Race, % c | ||||||
| Black | 50.9 | 50.9 | 39.0 | 58.3 | 72.7 | 44.9 |
| White | 41.5 | 42.3 | 51.3 | 33.3 | 21.6 | 46.9 |
| Other | 7.5 | 6.8 | 9.6 | 8.4 | 5.7 | 8.2 |
| Marital status, % c | ||||||
| Never married | 59.5 | 55.6 | 45.7 | 64.9 | 63.0 | 70.7 |
| Married/living with partner | 34.0 | 37.8 | 42.6 | 29.7 | 26.9 | 26.5 |
| Separated/divorced/widowed | 6.5 | 6.6 | 11.7 | 5.4 | 10.1 | 2.8 |
| Monthly individual income, % c | ||||||
| None | 19.0 | 17.2 | 17.3 | 29.9 | 22.7 | 15.6 |
| $1-800 | 32.5 | 30.6 | 29.7 | 35.3 | 34.2 | 35.7 |
| $801-1600 | 29.8 | 31.5 | 28.8 | 24.4 | 28.8 | 30.3 |
| ≥$1601 | 18.8 | 20.8 | 24.1 | 10.4 | 14.4 | 18.4 |
| Insurance, % c | ||||||
| None | 45.3 | 43.2 | 44.6 | 44.0 | 59.0 | 46.4 |
| Private | 41.4 | 42.4 | 43.0 | 31.1 | 31.7 | 47.9 |
| Public | 13.3 | 14.4 | 12.4 | 24.9 | 9.2 | 5.6 |
| Government support/trouble paying for basic necessities c d | 58.9 | 61.5 | 58.7 | 64.3 | 65.2 | 47.5 |
| Gravidity, % b | ||||||
| 0 | 27.0 | 19.5 | 22.6 | 30.1 | 24.7 | 44.9 |
| 1 | 22.2 | 20.1 | 14.5 | 29.8 | 24.1 | 25.3 |
| 2 | 18.3 | 21.8 | 17.7 | 14.0 | 16.1 | 14.4 |
| ≥3 | 32.5 | 38.7 | 45.2 | 26.1 | 35.1 | 15.3 |
| Parity, % c | ||||||
| 0 | 45.6 | 35.5 | 36.5 | 49.0 | 48.4 | 69.3 |
| 1 | 25.2 | 28.7 | 22.1 | 27.0 | 21.5 | 19.1 |
| 2 | 18.1 | 22.5 | 22.1 | 14.6 | 17.7 | 8.4 |
| ≥3 | 11.2 | 13.3 | 19.2 | 9.4 | 12.3 | 3.2 |
| No. of children desired, % c | ||||||
| Don’t know | 2.6 | 2.5 | 2.5 | 2.0 | 1.6 | 3.6 |
| 0 | 7.5 | 7.3 | 10.3 | 8.6 | 6.6 | 5.2 |
| 1 | 13.0 | 12.8 | 13.9 | 12.6 | 12.7 | 11.9 |
| No. of children desired, % c | ||||||
| 2 | 38.8 | 38.1 | 34.7 | 38.3 | 35.4 | 39.6 |
| ≥3 | 40.6 | 39.3 | 38.7 | 38.5 | 43.7 | 39.7 |
| History of sexually transmitted infection, % e | 33.7 | 35.1 | 31.1 | 34.4 | 42.7 | 28.1 |
| Lifetime sexual partners, % c | ||||||
| 0-1 | 9.3 | 8.3 | 8.3 | 13.2 | 6.6 | 10.8 |
| 2-4 | 26.8 | 26.9 | 20.1 | 32.0 | 28.8 | 26.1 |
| 5-9 | 32.4 | 32.5 | 31.1 | 29.2 | 36.4 | 33.2 |
| 10-19 | 19.6 | 21.0 | 21.9 | 14.4 | 17.1 | 19.5 |
| ≥20 | 11.9 | 11.3 | 18.6 | 11.3 | 11.1 | 10.3 |
| Sexual partners last 30 d, % c | ||||||
| 0 | 19.4 | 19.0 | 16.8 | 25.0 | 17.4 | 18.9 |
| 1 | 73.6 | 74.9 | 77.2 | 68.6 | 72.5 | 72.6 |
| ≥2 | 7.0 | 6.1 | 6.0 | 6.5 | 10.1 | 8.5 |
| Any unintended pregnancies, % f | 91.3 | 91.1 | 91.6 | 89.7 | 89.8 | 93.8 |
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