Life events and low birthweight--analysis by infants preterm and small for gestational age. Social stress was assessed in 92 women with low-birthweight babies and 92 controls using the detailed LEDS measure of life events and severe chronic difficulties. The low-birthweight group was divided into preterm delivery (n = 40), small for gestational age (SGA) (n = 40) and mixed groups. Multivariate analysis was performed using a binomial-logit model to examine whether social factors were independently and significantly associated with low birthweight once the effect of demographic factors, obstetric factors and smoking/drinking were taken into account. Comparison of preterm births with controls indicated that three factors were significantly associated: a previous low-birthweight baby, severe life event/difficulty and bleeding during pregnancy. For SGA babies the factors were: previous low-birthweight baby, low social support and smoking. By using a reliable measure of life events and adequate numbers of low-birthweight babies, this study overcame the potential inaccuracies of previous studies and indicates a more specific relation between social stress and low birthweight. 