The HPCS aims to examine whether differences in environmental exposures during different stages of pregnancy are independently associated with fetal growth in a large population of pregnant women in Israel, and to evaluate and compare multiple environmental exposures, including human biomonitoring and personal exposure to air pollution, in a nested panel of 150 pregnant women. Since 1998, information on all members’ interactions with Maccabi Healthcare Services (MHS) has been collected, including diagnoses, visits to primary and secondary care physicians, visits to outpatient clinics, hospitalizations, laboratory tests, and prescribed and purchased medications. The HPCS cohort potentially includes ~750,000 newborns born between 1998 and 2017 to MHS members.