The PGS is a longitudinal, community–based study of 2,451 girls who were initially recruited when they were between the ages of 5 and 8 years. Participants were recruited in 1999–2000 via random household sampling, with over-sampling of households in low resourced neighborhoods. The study consisted of yearly assessments that began early in development (ages 5–8 years) and extended into late adolescence/early adulthood (ages 17–20 years). In 2016, PGS researchers began a large-scale sub-study called PGS-ECHO, where any PGS participant who become pregnant or recently had a baby were invited to participate.