[Risk factors for low birth weight].

Low birthweight (LBW) is the main known determinant of infant mortality. In spite of the sharp decrease in infant mortality rates and of the rise in survival rates for children with LBW, no important decrease in LBW rates has been observed in Neuquen, Argentina. The purpose of this study was to try to understand the risk factors for LBW, the frequency of LBW in the population, and the role of prenatal care in its prevention, as well as to develop a risk factor scale that could be used to identify women at higher risk of giving birth to a child with LBW. With this in mind we performed a cross-sectional study based on 50% of the data entered into the Perinatal Information System for 1988-1995 by the 29 hospitals in Neuquen province (46,171 births). The distribution of birthweight and the frequency of potential risk factors for LBW were examined. The relationship between such factors and LBW was studied using a logistic regression model. On the basis of the results obtained, an additive scale was drawn up and validated with the remaining 50% of the data for registered births. The highest odds ratio (OR) was seen in women who had no prenatal care (OR = 8.78; 95%CI: 6.7 to 11.4). ORs for inadequate prenatal care, lateness in attending the first prenatal visit, preeclampsia or eclampsia, hemorrhage and anomalies of the placenta or placental membranes, and a history of a previous child with LBW were greater than 2.0. The risk of having children with LBW was also higher in women over the age of 40, women under 20, single women, smoking mothers, women with an intergenesic interval of less than 18 months, and women with a body mass index of less than 20. Finally, there was a direct linear relationship between points on the risk scale and the risk of having a LBW infant.