Background
It has been documented that maternal nutrition is associated with positive birth outcomes. This study was aimed at determining the predictors of healthy eating behavior among pregnant women in Qazvin, Iran in the context of the theory of planned behavior (TBP).
Materials and Methods
In this longitudinal study, 182 pregnant women who were referred to teaching hospitals in Qazvin in 2016 were recruited for participation. Data were obtained using TPB-specific questionnaires at baseline. The same pregnant women were asked to complete a food frequency questionnaire (FFQ) 3 months later. A series of hierarchical regression analysis was conducted to examine factors associated with healthy eating behavior among pregnant women.  
Results
The pregnant women reported low amounts of whole grain consumption and low-fat dairy product consumption. All TPB variables significantly predicted healthy eating behaviors at three-month follow-up. Perceived behavioral control (PBC) and behavioral intention were found to be the strongest predictors of healthy eating behaviors among pregnant women. The pregnant women’s subjective norms had the weakest relationship with healthy eating behaviors. The TPB model together with age provided a moderate to high explanation of consumptions in low-fat dairy products (R²=0.57, P<0.01), fruit (R²=0.30, P<0.01), vegetable (R²=0.28, P<0.01) and whole grains (R²=0.44, P<0.01).
Conclusion
The TPB explained significant variation in intention and healthy eating behaviors among pregnant women. Future studies should target on the PBC and intention to promote healthy eating behaviors among pregnant women.