The explicit use of theory in research helps expand the knowledge base. Theories and models have been used extensively in HIV-prevention research and in interventions for preventing sexually transmitted infections (STIs). The health behavior field uses many theories or models of change. However, educational interventions addressing contraception often have no stated theoretical base.
Review randomized controlled trials (RCTs) that tested a theoretical approach to inform contraceptive choice; encourage contraceptive use; or promote adherence to, or continuation of, a contraceptive regimen.
Through June 2013, we searched computerized databases for trials that tested a theory-based intervention for improving contraceptive use (MEDLINE, POPLINE, CENTRAL, PsycINFO, ClinicalTrials.gov, and ICTRP). Previous searches also included EMBASE. For the initial review, we wrote to investigators to find other trials.
Trials tested a theory-based intervention for improving contraceptive use. We excluded trials focused on high-risk groups and preventing sexually transmitted infections or HIV. Interventions addressed the use of one or more contraceptive methods for contraception. The reports provided evidence that the intervention was based on a specific theory or model. The primary outcomes were pregnancy, contraceptive choice or use, and contraceptive adherence or continuation.
Data collection and analysis
The primary author evaluated abstracts for eligibility. Two authors extracted data from included studies. For the dichotomous outcomes, the Mantel-Haenszel odds ratio (OR) with 95% CI was calculated using a fixed-effect model. Cluster randomized trials used various methods of accounting for the clustering, such as multilevel modeling. Most reports did not provide information to calculate the effective sample size. Therefore, we presented the results as reported by the investigators. No meta-analysis was conducted due to differences in interventions and outcome measures.
We included three new trials for a total of 17. Ten randomly assigned individuals and seven were cluster-randomized. Eight trials showed some intervention effect.
Two of 12 trials with pregnancy or birth data showed some effect. A theory-based group was less likely than the comparison group to have a second birth (OR 0.41; 95% CI 0.17 to 1.00) or to report a pregnancy (OR 0.24 (95% CI 0.10 to 0.56); OR 0.27 (95% CI 0.11 to 0.66)). The theoretical bases were social cognitive theory (SCT) and another social cognition model.
Of 12 trials with data on contraceptive use (non-condom), six showed some effect. A theory-based group was more likely to consistently use oral contraceptives (OR 1.41; 95% CI 1.06 to 1.87), hormonal contraceptives (reported relative risk (RR) 1.30; 95% CI 1.06 to 1.58) or dual methods (reported RR 1.36; 95% CI 1.01 to 1.85); to use an effective contraceptive method (reported effect size 1.76; OR 2.04 (95% CI 1.47 to 2.83)) or use more habitual contraception (reported P < 0.05); and were less likely to use ineffective contraception (OR 0.56; 95% CI 0.31 to 0.98). Theories and models included the Health Belief Model (HBM), SCT, SCT plus another theory, other social cognition, and motivational interviewing (MI).
For condom use, a theory-based group had favorable results in 5 of 11 trials. The main differences were reporting more consistent condom use (reported RR 1.57; 95% CI 1.28 to 1.94) and more condom use during last sex (reported results: risk ratio 1.47 (95% CI 1.12 to 1.93); effect size 1.68; OR 2.12 (95% CI 1.24 to 3.56); OR 1.45 (95% CI 1.03 to 2.03)). The theories were SCT, SCT plus another theory, and HBM.
Nearly all trials provided multiple sessions or contacts. SCT provided the basis for seven trials focused on adolescents, of which five reported some effectiveness. Two others based on other social cognition models had favorable results with adolescents. Of six trials including adult women, five provided individual sessions. Some effect was seen in two using MI and one using the HBM. Two based on the Transtheoretical Model did not show any effect.
Eight trials provided evidence of high or moderate quality. Family planning researchers and practitioners could adapt the effective interventions, although most provided group sessions for adolescents. Three were conducted outside the USA. Clinics and low-resource settings need high-quality evidence on changing behavior. Thorough use of single theories would help in identifying what works, as would better reporting on research design and intervention implementation.