Dr. Barrett studies the early origins of health and disease, or how exposures early in life shape our subsequent health and developmental trajectories. Because gestation is a particularly sensitive period when body systems are first forming, insults or exposures during this period may have profound downstream effects. Much of Dr. Barrett’s research focuses on prenatal exposure to endocrine disruptors, agents which interfere with the normal activity of hormones in the body. Phthalates are a class of endocrine disrupting chemicals that are found widely in food and consumer products. Nearly 100% of Americans have measurable levels of phthalate metabolites in their bodies, yet our current understanding of how these chemicals affect our bodies is limited. In The Infant Development and the Environment Study (TIDES), Dr. Barrett and colleagues are studying how prenatal exposure to these chemicals impacts reproductive and neurodevelopment, and whether the effects may differ in boys and girls. Other exposures, such as psychosocial stress, disrupt early development as well. Numerous studies have examined how stress during pregnancy may alter cortisol activity and “program” neurodevelopmental, metabolic, and immune outcomes. Much less is known about the extent to which prenatal stress (and related constructs, like anxiety) may also act through other pathways and mechanisms to affect the fetus. For example, evidence from animal models and humans suggests that prenatal stress may alter in utero androgen activity, thereby affecting sex-dependent development in the offspring. Dr. Barrett and collaborators are exploring this hypothesis in the Understanding Prenatal Signals and Infant Development (UPSIDE) Study, with an eye towards better understanding the early origins of sex differences. Concurrent work in this cohort will examine how maternal inflammation during pregnancy contributes to infant and child development. One of the major themes of this research is understanding the role of the placenta in communicating messages about stressors from mother to fetus (and vice versa).