The study began in Rome between June 2003 and October 2004 in health unites throughout the city. The study enrolled 704 women and 719 children, focusing on those whose mothers were older than 18 years, Italian citizens, and residents in the designated health unit. Factors such as low maternal education level and caesarean delivery were found to be significantly associated with refusal to participate, with 25 children eventually lost to follow-up, while mothers of those lost were more likely to have lower education levels and have smoked during pregnancy.