Our study design allowed equal surveillance for each
type of child care, and included children from 55 different
day care settings. The study groups provide a representative
sample of the spectrum of day care practices in
Pittsburgh, spanning different socioeconomic groups and
types and quality of day care settings. Likewise, a large
number of pediatric practices provided primary care for
these children. Recruitment of families that at the time of
the birth of the index child had specific plans for subsequent
child care led to the enrollment of many two-career
households. Accordingly, the study population was comprised
of individuals with a higher socioeconomic status
than the general population. Mothers of children in group