Marco Sanchez-Guerra1, Andres Cardenas2, Citlalli Osorio-Yáñez3. 1. Department of Developmental Neurobiology, National Institute of Perinatology, Mexico City, Mexico. 2. Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley. 3. Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de Mexico, Mexico City, Mexico.