Objectives and background: The aims of this study were to determine the values of birth weight, length and ponderal index of newborn infants with Down syndrome, to compare the categorization of these parameters according to different standards and to determine ponderal index values in this population. Patients and methods: The study included 141 newborns with the diagnosis of Down syndrome born at the Department of Gynecology and Obstetrics of University Hospital of Split from 1990. to 2015. Delivery room birth protocols were retrospectively reviewed and following data were collected: sex, gestational age, birth weight, birth length and ponderal index. The values of birth weight and length are categorized according to the standards for healthy children and children with Down syndrome. Ponderal index values are categorized according to gestational age standards. Results: In the observed period, 141 children with Down syndrome were born. Among the examined infants 52.5% were male and 47.5% were female. According to the standards for Down syndrome, 78.7% of subjects are classified as appropriate for gestational age (AGA) by their birth weight and 82.3% are classified as appropriate for age (AGA) by birth length. Ponderal index value is within the range of 10th to 90th percentile in 88.7% of subjects and corresponds to normal gestational age values. Newborn babies classified as small, appropriate and large for gestational age by their birth weight are significantly different in birth weight, length and ponderal index, regardless of the standards used for birth weight classification. Conclusions: Birth weight and birth length categorization is significantly different depending on the standards applied. By using syndrome specific standards most children are categorized in the appropriate for age group by their birth weight and length. The number of children classified as small or large for gestational age is lower when we use Down syndrome standards instead of standards for healthy children. Most of the subjects have normal ponderal index values. In order to suspect intrauterine growth restriction, correct birth weight categorization and ponderal index standards for Down syndrome in a specific population are required.