The Italian birth cohort known as NINFEA includes 7,500 pregnant women, recruited through the Internet from 2005 to June 2016, and their children. All pregnant women had enough knowledge of the Italian language to be able to answer the questionnaires. At baseline, 670 women were recruited from the city of Turin, Italy, from July 2005 to December 2006, with an average of 9.4 women recruited per week. Participants were older (average age of 33.3 years), of a higher educational level, more often primiparous, and more often born in Italy compared with all women delivering in Turin in the first semester of 2005. Following this pilot phase, the study extended to include pregnant women in the whole of Italy.