Introduction: Immigration, mainly from low socio-economic groups is a growing phenomenon in Latin America, including Chile. These groups may have a higher risk for obstetrical and neonatal pathology. Objectives: To know the rate of deliveries in immigrant mothers in Santiago, Chile and their demographics; To compare the weight and height of their children with that of native mothers (NM). Patients and Methods: In a case control studies a database of pregnant women delivering in the Obstetrics Service of San Borja - Arriarán Hospital was analyzed. For every case of an immigrant pregnant mother (IM) 2 control Chilean mothers (NM) were randomly selected, delivering n the same day in every case, between 1/06/2008 and 30/06/2009. Results: From a total number of 6441 deliveries, 495 were of immigrants (7.6 % of total rate; 89% Peruvians) compared with 976 controls. Pregnancy controlled in 97.9 % in IM and 99.1 % in NM (NS). A lower risk for teenage pregnancy was observed in IM (6.3 % versus 15.9 %; OR: 0.35; IC: 0.23-0.54); the national figure is 14%. No difference was observed in the rate of women older than 35 years old (15.0 vs 14.3 %), or in the primipara (45.8 versus 45.6%). IM had less low birth weight (5.4% versus 8.4%; OR: 0.62; IC 0.39-0.99) (national prevalence: 5.7%), without associations to lower teenage pregnancies. Conclusions: Immigrant mothers from low social-economic level in Santiago, Chile, show a lower proportion of teenage pregnancy and infants with low birth weight. There are no differences in the primiparity rate.