Using extended theory of planned behavior to understand aspirin adherence in pregnant women

Objective: To use the Theory of Planned Behavior (TPB) combined with action and coping planning plus global relationship with husband to explain the aspirin adherence in a sample of women with high-risk pregnancy. Methods: A total of 535 Iranian women (mean age = 32.29 +/- 4.98; year of marriage = 6.89 +/- 3.61) completed the study. Each participant filled out several questionnaires on TPB (i.e., a widely applied theory describing how behaviors are influenced by beliefs, attitudes, perceived behavioral control and behavioral intentions), action planning, coping planning and relationship with husband at baseline. Eight weeks later, each participant completed the Five-item Medication Adherence Rating Scale (MARS-5) and underwent the blood test on aspirin serum level to provide the subjective and objective aspirin adherence information, respectively. Structural equation modeling (SEM) was applied to test three proposed models on aspirin adherence. Results: The TPB with planning plus relationship with husband was supported (comparative fit index = 0.969; Tucker-Lewis index = 0.950). Behavioral intention was the mediator in the associations of aspirin adherence and the following variables: attitude, perceived behavioral control, and relationship with husband. Action and coping planning mediated the associations of aspirin adherence and the two variables of behavioral intention and perceived behavioral control. Relationship with husband mediated the association of subjective norm and aspirin adherence. Conclusions: The TPB model with (action and coping) planning plus relationship with husband serves a potential mechanism to explain the aspirin adherence for women with high risk of pregnancy. Possible implications are discussed based on our results.