title: Retrospectively sampled time-to-pregnancy data may make age-decreasing fecundity look increasing. European Infertility and Subfecundity Study Group.
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.
authors.affiliation: Department of Epidemiology and Social Medicine, University of Aarhus, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Juul
authors.forename: N
authors.initials: N
authors.lastname: Keiding
authors.forename: M
authors.initials: M
authors.lastname: Tvede
mesh_terms: D000328:Adult; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007246:Infertility / Q000453:epidemiology*; D008423:Maternal Age; D008875:Middle Aged; D009010:Monte Carlo Method; D011247:Pregnancy; D012189:Retrospective Studies; D013997:Time Factors