Factor Structure and Measurement Invariance Between Fathers and Mothers and Across Three Time Points After Childbirth: Identification of Core Items of The Japanese Version of The Mother-To-Infant Bonding Scale
Abstract Background The Japanese version of the mother-to-infant bonding scale (MIBS-J), a self-report of postnatal bonding disorder, is widely used in Japan. However, its psychometric properties, particularly measurement invariance, have rarely been reported, and the appropriateness of the use of the MIBS-J among perinatal fathers remains to be investigated. This study aimed to select and to validate MIBS-J items suitable for mothers and fathers at three time points (postpartum hospitalization period and 1 and 4 months postpartum) commonly used in clinical practice in Japan. Methods Postpartum mothers (n = 543) and fathers (n = 350) were surveyed at 5 days, 1 month, and 4 months postpartum. All participants were randomly divided into two subgroups, one for exploratory factor analyses (EFAs) and another for confirmatory factor analyses. Measurement invariance of the best model was tested using the entire sample, between fathers and mothers, and across the three observation periods. Results A three-item structure (items 1, 6, and 8) extracted through EFAs showed acceptable configural invariance. This model was accepted for scalar invariance between fathers and mothers and for metric invariance across the three time points. Conclusions This study showed that the three-item MIBS-J could be used reliably among Japanese parents in the first four postpartum months. Currently, all 10 MIBS-J items are used in clinical and research settings at various time points during the perinatal period. Our findings suggest that the MIBS-J with only three items is sufficient for diagnosis of postnatal bonding disorder, at least during the first four postpartum months.