The association between low birth weight and maternal smoking during pregnancy can be studied by obtaining smoking histories from women at the time of the prenatal visit and then subsequently correlating birth weight with smoking histories. What type of study is this? (AIIMS May 10)
|D||Case- control ( retrospective)|
This study is a cohort (prospective) study because the subjects (pregnant women) were categorized on the basis of exposure or lack of exposure to a risk factor (smoking during pregnancy), and then were followed to determine if a particular outcome (low-birth-weight babies) resulted.
a. The term cohort refers to the group of subjects who are followed forward in time to see which one develops the outcome.
b. Clinical trials are prospective studies in which an intervention is applied—no intervention was mentioned in the question.
c. In a case-control (retrospective) study of the relationship between low birth weight and maternal smoking, infants would be selected on the basis of low birth weight (cases) and normal birth weight (controls) and then the frequency of maternal smoking would be compared in the two groups. In cross-sectional studies exposure and outcome are measured at the same point in time. Correlation studies are used to compare disease frequencies between entire populations.