Time to pregnancy: reproducibility assessment in a retrospective cohort study

Abstract

Introduction: Time to pregnancy (TTP) is a clinical measurement of fecundity that has been used in occupational and environmental epidemiological research. Previous studies conducted in European women have shown an adequate reliability and reproducibility. However, these characteristics have not been yet evaluated in Latin American women. Objective: To assess the reproducibility of TTP for the first pregnancy as clinical measurement of couple’s fecundity in a population of Colombian women. Methods: A test-retest study of TTP in 27 Colombian women was nested in a retrospective cohort study assessing the effect of mercury exposure on reproductive effects. The questionnaire was applied twice by the same trained interviewer (by person at baseline and by phone 12 months later). The TTP’s reproducibility was evaluated using the intraclass correlation coefficient (ICC 2,k). Results: The median TTP was 4 months (Interquartile range 1-12). The range of time from the first pregnancy to the first interview was between 1 and 15 years. The ICC (2,k) was 0.726, (CI 95% 0.39 - 0.88), indicating good reproducibility between both measures. Conclusions: Our results suggest that TTP is a useful and reproducible measurement, with a remembrance time up to 15 years. Results were similar when assessed by phone and face-to face interview in a population of Colombian women.