2 Section of Biostatistics, Department of Public Health, University of Copenhagen, Copenhagen, Denmark Correspondence to Dr Anne-Marie Nybo Andersen; amny{at}sund.ku.dk Received 29 February 2012 Accepted 29 May 2012 Published 25 June 2012 Abstract Objectives To investigate the relationship between different indicators of socioeconomic position and the risk of spontaneous abortion. Design Cohort study. Setting 1996 -- 2002, Denmark. Participants All first time participants, a total of 89?829 pregnant women, enrolled in the Danish National Birth Cohort were included in the present study. Overall, 4062 pregnancies ended in spontaneous abortion. Information on education, income and labour market attachment in the year before pregnancy was drawn from national registers. Main outcome measure Spontaneous abortion, that is, fetal death within the first 22?weeks of pregnancy, was the outcome of interest. The authors estimated HRs of spontaneous abortion using Cox regression analysis with gestational age as the underlying time scale. Results Women with &lt;10?years of education had an elevated risk of spontaneous abortion when compared with women with &gt;12?years of education (HR 1.19 (95% CI 1.05 to 1.34)). The HR estimates for the four lowest income quintiles were all increased (HRs between 1.09 and 1.15) as compared with the upper quintile but did not differ considerably from each other. In general, no statistically significant association was found between labour market attachment and the risk of spontaneous abortion; however, the group of women on disability pension had an increased HR of spontaneous abortion when compared with women who were employed (HR 1.32 (95% CI 0.82