Description of the Cohort, Variables, and General Procedures

Abstract

The original Danish Perinatal Study, conducted during 1959 to 1962, provided us with an excellent set of data files well suited as a foundation for conducting both secondary analyses and additional prospective multidisciplinary inquiry. The perinatal study, originally designed to describe the risks to human reproduction from increasing background radiation, had a health focus with an exclusive emphasis on medical and biological variables [Zachau-Christiansen & Ross 1975]. However, the nature of the cohort and the broad scope of uniform and standard state-of-the-medical-arts measures at that time made it possible to consider additional analyses with diverse foci involving medical, familial, and environmental measures collected on the birth cohort during the first year of the index child’s life. The uniform conditions under which the initial data items were defined, organized, and collected constituted a major methodological strength, one that permitted in-depth evaluations of multiple variable relationships and a clearer understanding of the underlying associations. This study is in contrast with meritorious, but nonetheless for our purposes flawed, census-type studies in which data are collected by varied professionals in diverse locations possessing unspecified or unrecorded conditions, and subsequently aggregated for the purpose of providing broad descriptions of women and their pregnancies. Clearly, the nonuniform observation and data collection procedures would introduce an important methodological disadvantage in such studies.