Geração XXI (Generation XXI) is the first birth cohort assembled in Portugal. The sample of more than 8500 newborns was created between April 2005 and August 2006 in five public maternity units in Porto Metropolitan Area (Hospital S. João; Hospital Santo António; Hospital Pedro Hispano; Centro Hospitalar Vila Nova de Gaia and Maternidade Júlio Dinis).

The cohort aims to identify the characteristics of the pregnancy and the early childhood that might be associated with the children development and health status later in life.

Using a longitudinal approach, at 4 years of age children will be evaluated in a personal interview. It will be collected data about the child and the mother using structured questionnaires applied to the career (preferentially to the mother).

It will also be performed a physical evaluation that comprises detailed anthropometry, blood pressure measurements, a venous blood sample and dental evaluation.

The data collected will permit the characterization of children at 4 years of age and it will be possible to understand what characteristics of the pregnancy and early years of life influence health at 4 years of age, namely the determinants of childhood obesity.

The knowledge produced will allow the design of better strategies to prevent disease and to promote individuals health in Portugal, particularly the ones related to obesity and cardiovascular disease.

Current and future evaluations may be considered as ways of monitoring the health of Portuguese children contributing to plan better health polices and services, acting as a Health Observatory.