The MN cohort is one of three longitudinal birth cohorts set up by the CCCEH to examine the impact of environmental exposures on children’s health outcomes in minority populations living in New York City, the United States of America. The sample includes around 700 African American and Dominican mothers and their children living in the low-income New York City neighbourhoods of Northern Manhattan (Washington Heights and Harlem) and the South Bronx. The mothers were recruited during pregnancy through local prenatal clinics between 1998 and 2006. Enrolment was restricted to women aged range of 18 to 35 years who were non-active cigarette smokers; non-users of other tobacco products or illicit drugs; free of diabetes, hypertension, or known HIV; and had initiated prenatal care by the 20th week of pregnancy. The children’s health and development have been monitored yearly from birth through adolescence.