Original ArticleShift Work and Subfecundity: A European Multicenter StudyBisanti, Luigi MD; Olsen, Jørn MD, PhD; Basso, Olga MSc; Thonneau, Patrick MD, MSc, PhD; Karmaus, Wilfried MD, MPH The European Study Group on Infertility and SubfecundityAuthor Information From the Regione Lombardia Servizio di Epidemiologia, Milan, Italy (Dr Bisanti); The Danish Epidemiology Science Centre, Department of Epidemiology and Social Medicine, University of Aarhus, Aarhus, Denmark (Dr Olsen, Ms Basso); the Istituto di Scienze Sanitarie Applicate, Universitá degli Studi di Pavia, Pavia, Italy (Ms Basso); the World Health Organization and The Collaborative Center in Human Reproduction, INSERM U-292, Paris, France (Dr Thonneau); and the Institut für Gesundheitsforschung, NORDIG, Hamburg, Germany (Dr Karmaus). Address correspondence to: Luigi Bisanti, MD, Regione Lombardia Servizio di Epidemiologia, Via Stresa 24, 20125-Milano, Italy. Journal of Occupational & Environmental Medicine: April 1996 - Volume 38 - Issue 4 - p 352-358 Buy Abstract Shift work has been associated with various unfavorable pregnancy outcomes (ie, pregnancy loss, spontaneous abortion, low birth weight, etc). The suggested underlying mechanism is the interference of shift work with the circadian regulation of human metabolism and, in particular, with the temporal pattern of endocrine function. To analyze the effect of shift work on fecundity, the Time of Unprotected Intercourses (TUI) has been measured in couples recruited in the European Studies on Infertility and Subfecundity, which were undertaken in seven European countries. A low (odds ratio < 2.0) but consistent excess risk of subfecundity (TUI ≥ 9.4 months) has been observed both in a representative sample of the general population of women in reproductive age and in a sample of pregnant women or women who had just given birth. The excess risk was also consistently evident both in the subsample of the first pregnancies and in the subsample of the most recent pregnancies. Only the exposure of women to shift work seemed to affect a couple's fecundity; men working shift work did not modify the fecundity pattern of their own couples. No specific job title among shift workers concentrated the risk of subfecundity. No association of menstrual disorders with shift work was identified. Even though residual confounding could partly account for the results and the fact that a plausible biological explanation of the claimed effect is still lacking, data from this study are in favor of an association between shift work and prolonged waiting time to pregnancy. © Williams & Wilkins 1996. All Rights Reserved.