Early pregnancy loss (EPL), detected by patterns of human chorionic gonadotrophin (hCG) in urine, is the biomarker employed in investigations of the impact of personal, workplace or environmental reproductive toxins on human fertility. An issue central to these studies is what, in terms of urinary hCG expression, constitutes an EPL. This report describes the urinary molecular forms of hCG expressed in menstrual cycles in which a normal pregnancy was conceived, or an EPL occurred, or no apparent conception occurred. Qualitative and significant quantitative differences in the expression of hCG-associated analytes were found between normal pregnancy cycles and EPL cycles. Discriminant analysis calculation based on mole fractions of the different hCG-associated molecules afforded 91 per cent and 80 per cent correct classification of clinical pregnancy cycles and EPL cycles, respectively. Although hCG-associated molecules unique to either EPL or normal pregnancy were not found, what is thought to be an early form of hCG is expressed both at a high frequency and at a significantly higher concentration in early normal pregnancy when compared with EPL. The relative absence of this molecule very early in pregnancy may signal a pregnancy loss.