Patterns of exposure variability across pregnancy were examined for medical, lifestyle, residential, and occupational exposures in a population-based sample of 357 livebirths from 10 rural California counties.
A new measure of variability, the ratio of overall prevalence to time-window-specific prevalence, is introduced.
The higher the overall : time window (OTW) ratio, the greater the potential for misclassification when using anytime-during-pregnancy prevalence for an agent that exerts its effect in a smaller time window.
Exposures to cigarettes, marijuana, saunas/hot tubs, factors related to location of residence, and some workplace substances tended to be of longer duration.
Intertrimester concordance was high (kappa's>0.8) for smoking, residential proximity to crops, and use of video display terminals ; moderately high (kappa's between 0.4 and 0.8) for many occupational exposures ; and low (kappa's<0.4) for illnesses, which tended to be of short duration.
The lowest OTW ratios were for smoking and some residential exposures (1.1-1.3), while OTW ratios were much higher for paint applications, influenza, vaginal infections, and ultrasound (reaching, e.g., 4-6).
Use of anytime-during-pregnancy exposure indices can bias measures of association between risk factors and adverse pregnancy outcomes, particularly if the OTW ratio is high.
Misclassification bias occurs if there is a vulnerable time window during which the exposure exerts its effect.
Mots-clés Pascal : Epidémiologie, Méthodologie, Biais méthodologique, Gestation, Prévalence, Exposition professionnelle, Non professionnel, Mode de vie, Facteur milieu, Timing
Mots-clés Pascal anglais : Epidemiology, Methodology, Methodological bias, Pregnancy, Prevalence, Occupational exposure, Non occupational, Life habit, Environmental factor, Timing
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 96-0182801
Code Inist : 002B30A01A1. Création : 199608.