Why does the prevalence of low birthweight increase in Berlin?

Introduction: Infant and newborn mortality decreased in Germany during the last decade, while the prevalence of low birth weight increased. The object ive was to evaluate which risk factors for low birth weight might be respon sible for this increase. Material and Methods: Data of the Berlin Perinatal Statistics from 1993 thr ough 1999 on 181700 newborns were analysed by univariate and multiple logis tic regression equations. Results: From 1993 through 1999 the rate of birth weights below 2500 g in B erlin increased significantly from 6.9% to 7.5% per year (p<0.001). The pre valence of premature births increased significantly as well as that of mult iplets, of firstborns, of the mother's age, but also of their initial weigh t, height and body mass index. The prevalence of smokers in pregnancy was c onstant over this time period, the mean gestational age of newborns decreas ed significantly. By logistic regression equation 62% of the variance of lo w birth weight could be explained by the risk factors multiple birth, smoki ng in pregnancy, age of the mother, female sex, primiparity, German nationa lity, year of birth and additionally by the protective factors pregnancy du ration, initial weight of the mother, BMI, and weight gain in pregnancy. Conclusions: The increase in low birth weight over the last years can be ex plained by indicators of reproductive medicine.