A nationwide study of the effects of genes and the environment on children’s health will now extend into Bristol County, Mass.

The National Children’s Study, an unprecedented effort to follow 100,000 children from before birth to age 21, began a year ago. Brown University, in partnership with Women & Infants Hospital, in Providence, was among the study centers chosen last year to start the project. Brown researchers were awarded $14.1 million to gather data on 1,000 children in Providence County.

On Friday, the National Institutes of Health announced the 27 research locations for the next phase of the study. The Brown researchers will receive $12 million over five years to also study 1,000 families in Bristol County, Mass. They will work with Charlton Memorial Hospital in Fall River, St. Luke’s Hospital in New Bedford, Morton Hospital and Medical Center in Taunton, and Sturdy Memorial Hospital in Attleboro.

The study is the largest long-term examination of human health and development ever conducted in the United States. Researchers will visit thousands of randomly selected households, and recruit women who are pregnant or intending to become pregnant. They will then gather a variety of information, including biological samples from family members, and air, water, soil and dust samples from the environment. They will study everything from family history to diet to the characteristics of the neighborhood.

The result, researchers hope, will be a deeper understanding of what makes children sick and what keeps them healthy, and shed light on why autism, asthma, diabetes and obesity are increasing among America’s children.

Congress will pay for the project year by year. If the money comes through as expected, the first wave of recruitment will begin in the summer of 2010, and the preliminary findings will be available in 2012.