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Retrospectively sampled time-to-pregnancy data may make age-decreasing fecundity look increasing. European
1Department of Epidemiology and Social Medicine, University of Aarhus, Denmark.
Epidemiology (Cambridge, Mass.)
|October 31, 2000
Abstract:
The retrospective study based on pregnancy samples is the most commonly used method for studying time to pregnancy. Using a simple Monte Carlo simulation, this note focuses on a particular selection bias problem associated with this design: even if each woman's fecundity decreases with age, estimation of the effect of age may show the opposite trend. We recommend exercising increased caution in interpreting findings from pregnancy-based time-to-pregnancy studies.
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