An investigation, as part of a national study on anthropometric characteristics of livebirths, was carried out on 20,850 single livebirths born in 31 maternity hospitals in S. Paulo, Brazil, into risk factors for low birth weight (weight less than 2,501 gr.). The following factors were studied: maternal schooling, marital status, maternal age, parity, prepregnancy weight, smoking during pregnancy and prenatal care. Through multivariate analyses using log linear models, four significative risk factors for low birth weight were identified: "no prenatal care", prepregnancy weight < 50 kg", "smoking during pregnancy" and "maternal age < 20 years". The relative risk for "no prenatal care" was 3.4 in mothers with 8 or more years of schooling and 2.2 in mothers with less schooling. The risks associated with prepregnancy weight, smoking and maternal age were, respectively, 1.9, 1.7 and 1.4 and were found to be independent of maternal schooling. Considering simultaneously risks, magnitude and frequency of the risk factors in the population, it is evident that prepregnancy weight, smoking during pregnancy and prenatal care particularly for mothers with low socio-economic level, are factors whose control would result in considerable decrease in low birth weight incidence and, for that reason, they should be carefully considered by health intervention programs.
Low birth weight; Multivariate analysis; Maternal age; Prepregnancy weight; Smoking; Prenatal care
