Risk factors for persistent versus episodic mother-to-infant bonding difficulties in postpartum women in a nationwide Japanese longitudinal study

Background: The quality of mother-to-infant bonding (MIB) is a crucial determinant of nurturing behaviors and infant development, with bonding difficulties (MIBD) posing a substantial threat. While it is essential to identify MIBD risk factors, previous studies have generally examined MIBD at one time point, leaving the contributors to persistent MIBD uncertain. This study aims to discern longitudinal risk factors for persistent versus episodic MIBD. Methods: We evaluated 1833 postpartum Japanese women who delivered in the past twelve months, utilizing the Mother-to-Infant Bonding Scale (MIBS) and other sociodemographic, health, pregnancy, childbirth, and childrearing related data (T1). Follow-up data were obtained six months later (T2). MIBD was defined as a MIBS score of five or more, with "persistent" and "episodic" MIBD classified based on its occurrence at both or either one of the time points, respectively. Logistic generalized estimating equations and inverse probability weighting were used to identify risk factors and address selective attribution bias. Results: Of the subjects, 15.8 % reported episodic and 11.3 % reported persistent MIBD. Shared risk factors for both conditions included postpartum depression and low levels of family support (OR = 1.501-6.343). However, pre-pregnancy underweight status (OR = 1.698) was a unique risk factor for episodic MIBD, while first-time motherhood, no or discontinuation of breastfeeding, and later postpartum months (OR = 1.540-3.179) were distinctive risk factors for persistent MIBD. Conclusion: We identified both shared and unique risk factors for episodic and persistent MIBD. Particular attention should be afforded to persistent MIBD and early and proactive interventions to mitigate identified risk factors are recommended.