The MADRES cohort is an ongoing prospective pregnancy cohort of 1,000 predominantly lower-income Hispanic women in Los Angeles, California, in the United States of America. Enrollment in the MADRES cohort is initiated prior to 30 weeks of gestation through partnerships with four prenatal care providers in Los Angeles. Cohort participants are followed through their pregnancies, at birth, and through the infant’s first year of life through a series of in-person visits with interviewer-administered questionnaires, anthropometric measurements, and biospecimen collection, as well as through telephone interviews conducted with the mother.