Methods and compositions are provided for diagnosing ectopic pregnancy in a mammalian subject by detecting changes in expression of ISM2, ADAM12, PST1, PSG7, PST11, PSG9, PSG2 and other genes identified therein, including combinations thereof. A selected gene, gene transcript or protein/peptide expression product, or profiles or signatures formed by combinations of same, detected in a biological fluid of a subject, enables comparison of the corresponding genes, proteins or profiles from that of a reference or control having a normal intrauterine pregnancy. Detection of characteristic changes in the gene profile or protein expression signature of the subject is correlated with a diagnosis of ectopic pregnancy. Various compositions for use in such diagnosis include PCR primer-probe sets or ligands, labeled or immobilized, which are capable of detecting the changes in expression or translation of these targets.