Statistical and practical issues in the design of a national probability sample of births for the Vanguard Study of the National Children's Study.

The National Children's Study is a national household probability sample designed to identify 100,000 children at birth and follow the sampled children for 21 years. Data from the study will support examining numerous hypotheses concerning genetic and environmental effects on the health and development of children. The goals of the study present substantial challenges. For example, the need for preconception, prenatal, and postnatal data requires identifying women in the early stages of pregnancy, the collection of many types of data, and the retention of the children over time. In this paper, we give an overview of the sample design used in a pilot study called the Vanguard Study, and highlight the approaches used to address these challenges. We will also describe the rationale for the sampling choices made at each stage, the unique organizational structure of the NCS and issues we expect to face during implementation.