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IN UTERO ENVIRONMENTAL EXPOSURES IN THE NATIONAL CHILDREN'S STUDY - MEASUREMENT STRATEGIES
Citation:
QUACKENBOSS, J. J., P. MENDOLA, AND W. GALKE. IN UTERO ENVIRONMENTAL EXPOSURES IN THE NATIONAL CHILDREN'S STUDY - MEASUREMENT STRATEGIES. Presented at International Society for Environmental Epidemiology Annual Meeting, Paris, FRANCE, September 02 - 06, 2006.
Description:
The National Children¿s Study (NCS) is a longitudinal cohort study which is designed to follow a nationally representative sample of American children from prior to conception or early pregnancy until age 21 years. The Children's Health Act of 2000 directs a consortium of United States Federal agencies to: (1) evaluate the effects of both chronic and intermittent exposures on child health and human development; and (2) investigate mechanisms of developmental disorders and environmental factors that influence health and developmental processes to identify factors that are helpful, harmless and harmful. Exposures very early in pregnancy are difficult to measure directly because women may be unaware of their pregnancies and the logistics of timing and collecting samples during these early windows are challenging.
The NCS is focused on enrolling women who are likely to become pregnant as well as those early in pregnancy in order to assess the impact on child health and development due to in utero exposures that occur early in pregnancy. Couples planning pregnancy will be visited up to four times in the 6 months following enrollment (or moving into this group) to assess pregnancy status, exposures, and to collect biological specimens. Once pregnant, study visits are scheduled for each trimester: a home and clinic visit in the first trimester; a clinic visit in the second and third trimester. Environmental factors to be studied are prioritized based on the core hypotheses for the NCS which have been developed over the past five years with input from a variety of scientists and stakeholders (www.nationalchildrensstudy.gov). The NCS defines environment broadly including chemical, physical, biological, behavioral, and social factors, as well as genetic factors and their interactions with environmental exposures.
In order to evaluate the effects of both chronic and intermittent exposures, the Study needs to develop approaches to capture the frequency, magnitude, and duration of peak or intermittent exposures and carefully consider the impact of these measures on both participant burden and Study costs. Approaches for exposure assessment in the NCS will likely involve a combination of environmental and biological samples, together with questionnaire and diary reporting. A strategy for their use is based on two related concepts: 1) core measures obtained for the entire cohort and the use of validation sub-samples for more detailed exposure measurements (i.e., for measurement error adjustment); and 2) a hierarchical approach that relates measures obtained at different levels of aggregation (e.g. individual, residential, community, and region). A comprehensive pilot study will assess the feasibility of enrolling women using a household-based screening approach and will demonstrate the acceptability of biologic and environmental sample collection during pregnancy.