Aim: The rapid decline in Iran’s total fertility rate over recent decades has become a major demographic concern. This study aimed to evaluate the effect of motivational interviewing, based on the Theory of Planned Behavior (TPB), on childbearing intention among women with one child.

Methods: This Randomized Controlled study was conducted in 2025 among 90 women with one child attending comprehensive health service centers in Bijar, Iran. Participants were randomly assigned to intervention (n = 45) and control (n = 45) groups. Data were collected using a demographic and a TPB-based childbearing intention questionnaire. The intervention group participated in six motivational interviewing sessions (45–60 minutes each), while the control group received routine care. Outcomes were assessed at baseline, immediately after the intervention, and three months later. Data were analyzed using independent t-tests, repeated-measures ANOVA, in SPSS version 27.

Results: The mean age in the intervention and control groups was (35.62 ± 6.43 vs. 35.86 ± 5.49 years). At baseline, no significant differences were observed between the groups regarding demographic characteristics or TPB construct scores (P > 0.05). The intervention group demonstrated significant group-by-time effects for perceived behavioral control and childbearing intention (P < 0.001). Although attitude and subjective norms changed significantly over time, the group-by-time interactions were not statistically significant for either construct .

Conclusion: Theory-based motivational interviewing effectively enhanced childbearing intention among women with one child. Incorporating motivational interviewing into reproductive health services may promote informed decision-making regarding childbearing and support fertility promotion policies.