Fetal and early postnatal lead exposure measured in teeth associates with infant gut microbiota

•We examined associations of Pb (measured in baby teeth) and infant gut microbiota.•Pb was measured before and after birth; stool was collected at 1- and 6-months.•Fetal Pb associated with 1-month Candida, Aspergillus, Malassezia, and Saccharomyces.•Pb did not associate with overall structure of infant gut bacterial communities.•Yet, some bacteria (e.g., Collinsella, Bilophila, Bacteroides) associated with Pb. Lead (Pb) is an environmentally ubiquitous heavy metal associated with a wide range of adverse health effects in children. Both lead exposure and the early life microbiome— which plays a critical role in human development—have been linked to similar health outcomes, but it is unclear if the adverse effects of lead are partially driven by early life gut microbiota dysbiosis. The objective of this study was to examine the association between in utero and postnatal lead levels (measured in deciduous baby teeth) and early life bacterial and fungal gut microbiota in the first year of life. Data from the Wayne County Health, Environment, Allergy and Asthma Longitudinal Study (WHEALS) birth cohort were analyzed. Tooth lead levels during the 2nd and 3rd trimesters and postnatally (