This study was designed to determine the factors resulting in low birth weight. A hospital cross-sectional retrospective study was carried out in the Ratchaburi Hospital, Ratchaburi province. The main objective of this study is to identify factors and conditions which result in low birth weight. Data was collected from delivery records of the hospital. There were 141 cases of the mothers who delivered low birth weight infants and 135 cases of normal birth weight among 276 cases were randomly selected. Data analysis was done by using spss program The data statistical method used was Chi-square, frequency, mean, standard deviation, odds ratio and correlation. The result of the study show that socio-economic biological factors, medical conditions and complications of pregnancy factors that there were significant association with LBW infants. According to the study findings, it is recommended that all pregnant women need access to basic antanatal health care. Health personnel should give health education about the pregnancy and increase the availability of early and regular high-quality prenatal care. the enhance the awareness of the complication of the multigraviadous women, the health personnel must add the information on ghigh risk factors in health education during ANC. Emphasizing the importance of antenatal care the midwifery curriculum. Improving the supervision system for MCH service activities with special emphasis on the factors found to be associated with LBW.