OBJECTIVE: To identify the risk factors associated with low birth weight (<2500 grams). METHODS: Unmatched case-control study performed in a tertiary maternity hospital in Campinas, Brazil, involving 43,499 liveborn infants delivered in the institution between 1986 and 2004. Analysis of the database containing information on deliveries of women who gave birth to infants with low (6,477 cases) and normal (37,467) birth weight were performed. Factors associated with low birth weight were identified according to the odds ratio (OR) and 95% confidence interval (95%CI) in the bivariate analysis and according to the adjusted OR in the multivariate analysis. Sociodemographic characteristics, reproductive history, previous morbidity and factors related to current prenatal care were studied. RESULTS: Extremes of reproductive age, poor education, low maternal weight, smoking beyond the fourth month of pregnancy, previous cesarean section, interdelivery interval <24 months and >37 months, maternal history of hypertension, cardiopathy and premature delivery, few (<5) prenatal visits and beginning prenatal care late in pregnancy (after the 3rd month), premature rupture of membranes, increased blood pressure, infectious diseases and hemorrhages during current pregnancy were all associated with low birth weight. Maternal obesity and being a primipara were found to be protective factors. CONCLUSION: These results confirm the findings of previous studies. The detection and prenatal management of modifiable factors, counseling, pre-conception intervention, adequate prenatal care and the implementation of primary and secondary prevention of maternal morbidity should be a target for all obstetrician as a potential source for reducing the incidence of low birth weight.
Birth Weight; Risk factors; Maternal welfare; Prenatal care