<jats:p>Pregnancy loss predominantly occurs during the first 3–4 weeks due to fertilization failure or early embryonic losses in cattle. Insufficient biochemical communication between conceptus (embryo plus extraembryonic membranes) and endometrium has been suspected as the primary cause for early embryonic losses. If molecules regulating this communication were identified, molecular mechanisms associated with early pregnancy losses could be better understood. To identify candidate molecules as detection markers of non-pregnant or females undergoing embryonic loss, peripheral blood from embryo-transferred heifers on day 7 (day 0 = day of estrus) were collected on days 17 (pre-attachment), 20 (during attachment), and 22 (post-attachment), which were subjected to metabolome and global proteome iTRAQ analyses. The metabolome analysis partly divided serum components into pregnant or not. In the iTRAQ analysis, heatmap analysis with top 25 proteins was separated into pregnant or not on day 20 or 22. Furthermore, receiver operating characteristic curve (ROC) analysis identified five candidate proteins detecting non-pregnant heifers, of which SNX5 in day 22 serum had the highest area under the curve (AUC): 0.983. We also detected SNX5 in day 22 serum from non-pregnant heifers using western blotting. These results suggest that high SNX5 in day 22 serum could predict early pregnancy loss in heifers.</jats:p>