On February 26th of 2019, an online meeting was held with the primry investigator and managerial and executive members of the PERSIAN Birth Cohort. In this meeting, the procedure of collecting biological samples, including breast milk, hair, nail and urine, in each city were reviewed. Then an application called “Dental Cohort” was introduced by Rafsanjan's managerial members. Also, the suggested proposal for placental sampling were deliberated, and members were asked to declare their ideas and suggestions for new sub studies. At the end, the process of data pooling was discussed.