Neonatal transfer and duration of hospitalization of newborns as potential risk factors for impaired mother-infant bonding: The Japan Environment and Children's Study

Background: Currently, there is no consensus regarding the relationship between neonatal transfer and duration of hospitalization in cases of impaired mother -infant bonding (MIB). This study aimed to determine whether neonatal transfer and duration of hospitalization of newborns increase the risk for impaired MIB. Methods: The MIB Scale was used to assess impaired MIB 1 year after delivery, using data from the Japan Environment and Children 's Study. A score >= 5 points indicated impaired MIB. Multiple logistic regression analyses were performed to estimate the association between neonatal transfer and duration of hospitalization of newborns with the risk of impaired MIB. Results: A total of 66,402 pregnant women were included in the study. The overall incidence rate of impaired MIB was 11.2 %. The mean duration of hospitalization of newborns was 7.1 +/- 6.4 days. After adjusting for potential confounders, neonatal transfer (adjusted odd ratio (OR): 1.13 [95 % confidence interval (CI)), 1.01 -1.27]) and duration of hospitalization of newborns (adjusted OR 1.007; 95 % CI 1.003 -1.010) were associated with impaired MIB. The area under the receiver operating characteristic curve for the duration of hospitalization of newborns for impaired MIB was 0.53. Limitations: Maternal childhood abuse and neglect history were not evaluated, and information regarding whether the infants were admitted to the neonatal intensive care unit was unavailable. Conclusions: Japanese women whose newborns underwent neonatal transfer should be followed up for at least 1 year after delivery, regardless of the duration of hospitalization of newborns.