Not only preterm delivery arid low birth- weight will increase infant morbility and mortality, large for gestational age (LGA) babies will also have higher morbility rate than normal group. After excluding maternal medical diseases, this study is to analyze the relationship of maternal demographic data, health practices, and maternal psychosocial factors to fetal birthweight. We herein collected 131 available guestionnaires from the LGA group mothers and 138 from the normal birthweight group mothers, then analyzed the data with stepwise discriminant procedure. Results indicate that the independent varibles for LGA babies are maternal demographic data (parity, weightgain during pregnancy, and prior pregnancy history), usual body weight before pregnancy and social support for psychosocial factor. This survery finds out factors that relate with baby birthweight and emphasizes the important influence of maternal health behavior and soical support on the weight.