Background: Psychosocial events experienced by pregnant women could have an effect on the newborn. Aim: To study the effects of psychosocial events during pregnancy on the birth weight and gestational age of the newborn. Material and methods: One hundred ninety two pregnant women, coming from urban and rural areas, were interviewed at about 35 weeks of gestation. Information from the obstetrical chart was obtained and different inquiries were applied, about personal history, socioeconomic level, emotional state, vital events, family and social support. Results: Fifty six percent of interviewed women did not plan their pregnancy, 32% considered their pregnancy as a negative event in their life, 62% had symptoms of emotional distress and 81% were unsatisfied with the social support that were receiving. When psychosocial factors were included in the multiple regression analyses, their predictive power for birth weight and gestational age improved. Including these variables, the R2 for birth weight was 0.22 and for gestational age, 0.18. Conclusions: Psychosocial factors during pregnancy are important predictors of birth weight and gestational age of the newborn. Measures should be taken to reduce the impact of these factors on the product of pregnancy (Rev Méd Chile 2002; 130: 561-68)