Once the maternal interview was completed, participants were randomly assigned to either intervention or usual care.
However, the comparison of the analysis of the biological samples from children with and without maternal interview was similar.
A maternal interview was conducted to document information on demographic background, smoking, alcohol and drug use during pregnancy, and other maternal characteristics.
A maternal interview was conducted to provide information on demographic background and other factors including smoking and alcohol and drug use during pregnancy.
The following variables obtained from the maternal interview were identified as potential confounders through directed acyclic graph analysis (Greenland et al. 1999) and included in the final adjustment set: maternal age, race/ethnicity, educational attainment, household income, tobacco smoking in the first month of pregnancy, alcohol consumption during the first trimester, and maternal nativity.
Maternal interviews were completed for 240 cases (69%).
Postnatal maternal interviews were administered in person when the child was 6 months and annually thereafter to determine any changes in residence, exposure to ETS, and other health or environmental conditions.
In the structured maternal interview, which was conducted without knowledge of the clinical findings, systematic information was collected on maternal employment, including exposure conditions and the use of personal protective equipment.
Maternal interviews (2000 2002) were done by trained workers, and completed forms were checked by field supervisors for errors.
The database of the physician survey and the database of maternal interviews will be combined for statistical analyses at group level.
