Background: Sentinel sites in nutritional surveillance during pregnancy have been used between 1997 and 2001. In this paper evolution trends of selected indicators are presented and the influence of sociodemographic variables on the distribution are analysed. Methods: Expert criteria led the selection of the sentinel sites, which were distributed in the administrative Health Areas with the highest and the lowest rates for low birth weight scattered through the 15 provinces in the country. Evolution trends in chronic energy deficiency and overweight at the beginning of pregnancy were measured according to BMI values; inadequate weight gain during pregnancy and evolution of anaemia during the third trimester of pregnancy were ascertain as well. Results: Study results show an increase in overweight at the beginning of pregnancy about 27%, a decreasing trend in the proportion of pregnant women with inadequate weight gain after an intervention in this population subgroup and a decreasing trend in the proportion of pregnant women with anaemia mainly during the first trimester of pregnancy.