This study examined how prepregnancy body mass index (BMI) relates to healthy eating and physical activity during pregnancy through body image and self-efficacy. Data from 369 Korean women in their third trimester were analyzed using validated instruments. Serial mediation analyses indicated that BMI was indirectly related to healthy eating through body image and self-efficacy, with no direct effect. In contrast, BMI showed both a direct association and a sequential indirect effect on physical activity through these psychological factors, while self-efficacy alone was not a mediator. These findings suggest that healthy eating is more strongly influenced by psychological perceptions, whereas physical activity may respond more directly to BMI-related cues or external guidance. Assessing body image and self-efficacy during prenatal care may help healthcare professionals support women, particularly those with elevated BMI, in maintaining healthy behaviors during pregnancy.
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