SHIFT WORK AND SUBFECUNDITY - A EUROPEAN MULTICENTER STUDY

Shift work has been associated with various unfavorable pregnancy outc omes tie, 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 w ith the temporal pattern of endocrine function. To analyze the effect of shift work on fecundity, the Time of Unprotected Intercourses (TUT) has been measured in couples recruited in the European Studies on Inf ertility and Subfecundity, which were undertaken in seven European cou ntries. A low (odds ratio < 2.0) but consistent excess risk of subfecu ndity (TUI greater than or equal to 9.4 months) has been observed both in a representative sample of the general population of women in repr oductive age and in a sample of pregnant women or women who had just g iven birth. The excess risk was also consistently evident both in the subsample of the first pregnancies and in the subsample of the most re cent pregnancies. Only the exposure of women to shift work seemed to a ffect a couple's fecundity; men working shift work did not modify the fecundity pattern of their own couples. No specific job title among sh ift workers concentrated the risk of subfecundity. No association of m enstrual disorders with shift work was identified. Even though residua l confounding could partly account for the results and the fact that a plausible biological explanation of the claimed effect is still lacki ng, data from this study are in favor of an association between shift work and prolonged waiting time to pregnancy.