Individual, Interpersonal, and Obstetric Factors Associated with Exclusive Breastfeeding Among Polish Mothers: A Cross-Sectional Study Informed by the Socio-Ecological Model

Background/Objectives: Exclusive breastfeeding (EBF) is associated with multiple individual, interpersonal, and healthcare-related factors. Identifying potentially modifiable factors associated with EBF across different levels of influence may help inform future breastfeeding research and support strategies. This study aimed to identify individual, interpersonal, and obstetric factors associated with exclusive breastfeeding among Polish mothers, using the Socio-Ecological Model (SEM) as a conceptual framework. Methods: A cross-sectional online survey was conducted among 769 Polish mothers of children aged up to 24 months. The questionnaire included sociodemographic and perinatal characteristics, as well as standardized instruments: Multidimensional Scale of Perceived Social Support (MSPSS), Iowa Infant Feeding Attitudes Scale (IIFAS), and Birth Satisfaction Scale–Revised (BSS-R). Hierarchical binary logistic regression was used to identify factors associated with exclusive breastfeeding. Missing data were handled using multiple imputation by chained equations, with 20 imputed datasets, and estimates were pooled according to Rubin’s rules. Results: Exclusive breastfeeding was reported by 610 participants (79.3%). Across the 20 imputed datasets, the final model showed χ2 values ranging from 62.92 to 70.00 and Nagelkerke’s R2 values ranging from 0.123 to 0.136. In the final model, mode of delivery (OR = 1.92, 95% CI: 1.32–2.80, p < 0.001), complications/illnesses during pregnancy (OR = 1.73, 95% CI: 1.14–2.64, p = 0.011), and partner encouragement (OR = 2.81, 95% CI: 1.72–4.59, p < 0.001) were significantly associated with exclusive breastfeeding. A nonlinear association between breastfeeding attitudes and exclusive breastfeeding was observed, with the quadratic IIFAS term remaining statistically significant (OR = 0.99, 95% CI: 0.99–1.00, p = 0.002), whereas the linear IIFAS term was not statistically significant in the final model (OR = 1.04, 95% CI: 1.00–1.08, p = 0.078). Birth satisfaction and the MSPSS Friends, Family, and Significant Other subscales were not independently associated with exclusive breastfeeding in the final model. Conclusions: Among the variables included in the final model, partner encouragement showed the strongest association with exclusive breastfeeding. Mode of delivery and complications/illnesses during pregnancy were also associated with exclusive breastfeeding, while the association between breastfeeding attitudes and exclusive breastfeeding was nonlinear. These findings may inform future prospective and intervention studies examining partner support, breastfeeding attitudes, and perinatal factors in relation to exclusive breastfeeding. Further research is warranted to explore the mechanisms underlying the observed associations.