The National Children’s Study (NCS) is the largest and most comprehensive study of children’s health and development in the United States.  The NCS was authorized by the Children’s Health Act of 2000 and is led by the U.S. Department of Health and Human Services—through the National Institutes of Health and the Centers for Disease Control and Prevention—and by the U.S. Environmental Protection Agency.  The NCS will enroll a representative sample of 100,000 children and their families who will be followed from before conception or early in pregnancy until age 21. The goal of the NCS is to provide information that will ultimately lead to improvements in the health, development, and well being of children. The primary aim is to investigate the effects of environmental exposures (chemical, biological, physical, psychosocial) as well as gene-environment interactions on pregnancy outcomes, child health and development, and precursors of adult disease. NCS hypotheses have been used to guide development of the study design and sample size, and assure that important research questions can be addressed.  The NCS Study’s Research Plan describes the study’s background, design, and measures, and the rationale for their selection and is available at http://nationalchildrensstudy.gov/research/research_plan/
The NCS will employ a national probability sampling approach to select locations for conduct of the study.  A sample of 105 locations, generally single counties, was randomly selected from all U.S. counties.  Seven locations will participate in the pilot phase of the NCS with other locations to begin enrollment after the pilot phase has been completed.  Pregnant women and their partners, and women of childbearing age, comprise the initial target population for enrollment in each study Location.  The frequency and type of initial follow-up, for women who are enrolled in the Study prior to pregnancy, will depend on the woman’s probability of pregnancy.  Once pregnant, a minimum of six in-person study visits are planned from the first trimester of pregnancy through three years of age. Three of these visits are in the home, and three are in a clinical setting (one of which is the place of delivery of the infant).  After age three years, it is anticipated that in-person visits will occur every two to three years, with an additional home visit after each change of permanent residence. Remote data collections, e.g., telephone, computer, or mail-in questionnaires, will occur in between face-to-face contacts.
The NCS is in a unique position to answer many questions regarding the effects of environmental exposures on the long-term health of children. The focus on exposures prior to and early in pregnancy is a unique feature of this study, as is the breadth of planned exposure and outcome measurements. The NCS will answer important questions related to the environment and children’s health, and so will provide the foundation for government policy, nursing and medical practice, and individual decisions that will improve the overall health of children.