Acta Medica Okayama 1342-078X 19 2 2014 Promoting factors of physical and mental development in early infancy: a comparison of preterm delivery/low birth weight infants and term infants 160 EN Kaori Hayashida Mikiya Nakatsuka The aim of this study was to assess correlations between various factors and the physical and mental development of 4-month-old infants using a multi-faceted evaluation approach. A total of 1,402 self-administered questionnaires were distributed to consenting mothers of infants who had undergone a 4-month health checkup in Hiroshima prefecture, Japan. The questionnaires included items from the Japan Child and Family Research Institute Child Rearing Support Questionnaire and the KIDS type A test. Of the 421 completed questionnaires on mother-child pairs that were returned, 318 met the inclusion criteria and were eligible for further analysis. Comparison between infants in a preterm delivery or low birth weight (LBW) group (preterm and/or LBW group; n = 31) and a term delivery appropriate-weight for date (AFD) infant group (term AFD group; n =287) revealed that the preterm and/or LBW group had significantly higher mother child-rearing anxiety and difficult baby scores, along with significantly lower infant development and motor skill scores. Within the term AFD group, infants of primiparous mothers had significantly higher scores for motor skill and sociability with adults than those of multiparous mothers. Language comprehension scores were significantly higher in infants that were exclusively breast-fed than those formula-fed or combined breast-fed and formula-fed. Verbalization scores of infants whose mothers worked were significantly higher than those of infants whose mothers did not work. Infants with siblings aged < 4 years exhibited significantly lower scores for motor skills, verbalization, and sociability with adults than infants without siblings or with siblings aged at least 5 years. In particular, we found that a mother's child-rearing anxiety was related to many areas of infant development. Evaluating the absence or presence of such factors and conducting preventive treatment could promote healthy infant development. No potential conflict of interest relevant to this article was reported.