The Edinburgh Postnatal Depression Scale (EPDS) is a widely used screening tool for post-natal depression (PND). Recent factor analytic investigations of the EPDS have suggested the instrument may be useful in the prediction of PND as the instrument appears to be multidimensional, thus facilitating sub-scale development for this purpose. The psychometric properties of the EPDS were evaluated in women in the third trimester of pregnancy. Confirmatory factor analyses found support for the multidimensionality of the instrument; however, there was clear variability in model fit to data suggesting previous reports of the stability of the underlying factor structure of this instrument may be over-optimistic. The potential for development of the EPDS as a predictive screening measure of PND is likely to be optimistic because of variability in the factor structure of the instrument over the course of pregnancy and in the post-natal period.