The Italian NAC-II study is a part of the ‘Public health impact of long-term, low-level, mixed element exposure in susceptible population strata’ (PHIME) project, which includes four birth cohorts from Italy (NAC-II), Slovenia, Greece, and Croatia. The aim of the study is to investigate the association between low-level mercury exposure from food consumption in pregnancy and child neurodevelopment, with follow-up until seven years in the NAC-II cohort. Participants at baseline assessment were 900 pregnant women recruited from Burlo Garofolo Children’s Hospital in Trieste, Italy, who had lived in the area for at least two years. Baseline assessments took place when the women were between 20 and 22 gestational weeks, with subsequent waves including children until they were seven years old.