Background: The behavioral immune system (BIS) comprises psychological mechanisms that detect potential pathogen threats and promote behaviors that reduce the risk of infection. Although previous research has primarily examined BIS responses in relation to individuals’ own vulnerability to disease, relatively little attention has been given to whether the vulnerability of genetic relatives, particularly offspring, may influence maternal pathogen-avoidance responses. The present study examines whether offspring age and preterm status are associated with maternal BIS responses and hygienic behaviors, and whether caregiving-related factors moderate these associations.

Methods: A total of 172 Iranian women will participate in the study, including 86 mothers with children aged up to 60 months and 86 women in a comparison group. BIS responses are assessed using measures of disgust sensitivity, germ aversion, and perceived infectability, while child-directed hygienic behaviors are assessed using a researcher-developed questionnaire. Among mothers of children under 60 months, separate multiple linear regression analyses examine whether child age and preterm status predicted BIS-related responses and hygienic behaviors, controlling for maternal immunosuppressant use and autoimmune conditions. Separate moderation analyses examine whether daily contact duration, maternal affection, and relationship quality moderated the associations of child age and preterm status with BIS-related outcomes.