The National Institute of Child Health and Human Development (NICHD) serves as the lead agency for the National Children?s Study (NCS or Study), a longitudinal cohort study that will examine the effects of environmental influences on the health and development of approximately 100,000 children. Environment is broadly defined to include biological, physical, chemical, and social/cultural influences on children?s health and development. The goal of the Study is to provide information that will ultimately lead to improvements in the health, development, and well being of children. Enrolled children will be followed from before birth until the age of 21 years. Additional background about the Study is available on the Study?s Website (www.nationalchildrensstudy.gov ). The Study began in a pilot or Vanguard phase in 2009, expanding in 2010 to include 37 Vanguard locations. Due to contract expiration and changes in study implementation, new awards at these locations will be made later in 2012. The purpose of these new contracts will be to conduct an orderly and complete transition of all Study Center activity to a successor Contractor only. There will not be any data and/or specimen collection activities during this contract period. The new contract awards will be for a 6 month period beginning on September 28, 2012 and continuing on through March 31, 2013.