The effect of a theory of planned behavior-based education model on self-management and metabolic control in pregnant women with gestational diabetes: a randomized controlled trial

Abstract

Background: Gestational diabetes mellitus (GDM) is a common pregnancy complication associated with adverse maternal and neonatal outcomes. Lifestyle modification is central to GDM management; however, optimal strategies for supporting self-management remain unclear. This study evaluated the effect of a personalized Theory of Planned Behavior (TPB)-based online education model supported by motivational interviewing (MI) on behavioral determinants and metabolic control in women with GDM.

Methods: This randomized controlled trial was conducted in a public maternity hospital in Istanbul, Türkiye, with 66 pregnant women with GDM (intervention: n = 33; control: n = 33). Data were collected using the Gestational Diabetes Intention, Attitude, and Behavior Questionnaire (GDIAB-Q), a sociodemographic and clinical form, and medical records. Co-primary outcomes were changes in five GDIAB-Q subscales (attitude, subjective norm, perceived behavioral control, intention, and planning). Secondary outcomes included metabolic parameters (postprandial blood glucose, HbA1c, lipid profile, blood pressure, and body mass index). The intervention group received three TPB-based online sessions with MI during gestational weeks 28-30; controls received usual care. Effect sizes (Cohen's d) and 95% confidence intervals were calculated. The study was registered at ClinicalTrials.gov (NCT04874922).

Results: The predefined theory-informed success criterion for the co-primary outcome set was met. Significant between-group improvements were observed in attitude (d = 0.71, 95% CI: 0.21-1.21, p = 0.005), subjective norm (d = 0.80, 95% CI: 0.30-1.30, p = 0.002), and intention (d = 0.56, 95% CI: 0.06-1.05, p = 0.028). No significant differences were found for perceived behavioral control or planning. Secondary outcomes favored the intervention, with lower postprandial blood glucose (d = 0.51, p = 0.045), HbA1c (d = 0.50, p = 0.045), and BMI (d = 0.59, p = 0.021).

Conclusion: This TPB-based online education model strengthened key behavioral determinants of self-management and was associated with early improvements in selected metabolic outcomes among women with GDM. Theory-driven, personalized education may support GDM self-management; longer-term follow-up is needed to assess sustained effects.

Keywords: Diabetes education; Gestational diabetes; Lifestyle modification; Midwifery; Motivational interviewing techniques; Nursing; Theory of planned behavior.