Risk factors for low birthweight in Japanese infants.

The purpose of our study was to identify risk factors for low birthweight (LBW; birthweight < 2500 g) in Japanese infants. The data was collected from questionnaires completed by the parents of 23132 infants who underwent a standardized well baby check-up for 1-month-old infants, conducted by the Fukuoka City Medical Association from 1987 to 1995. The following eight factors and their second-order interaction terms were examined as potential risk factors for LBW: maternal age at delivery, history of live-born LBW infant, history of abortion in previous pregnancies, maternal smoking, coffee and alcohol consumption during pregnancy, prenatal training and live birth order. The results of multiple logistic regression analysis showed that the following three factors and one interaction term significantly contributed to LBW: history of live born LBW infant, maternal smoking, live birth order and the interaction between maternal smoking and live birth order. The smoker-related risk for LBW was quite different in each of the three groups stratified by live birth order. Efforts should be made, for example, to increase the accessibility of early, high-quality prenatal care for the high-risk groups with previous LBW babies and to implement smoking intervention, ranging from specific medical procedures to broad-scale public health and health-related educational programs in schools.