Background: Ectopic pregnancies associated with negative urine or serum pregnancy test by radioimmunoassay usually demonstrate either nonviable trophoblast or absent production of beta-hCG by the ectopic pregnancy.
Case: We report a patient with intra-abdominal hemorrhage caused by a ruptured ampullary ectopic pregnancy who had undetectable serum and urine beta-hCG levels (less than 5 mIU/mL). Immunoperoxidase staining of the ectopic trophoblastic tissue obtained at surgery revealed both beta-hCG and placental alkaline phosphatase.
Conclusion: Negative serum and urine pregnancy tests can occur even though beta-hCG produced by the viable ectopic trophoblastic tissue can be demonstrated by immunoperoxidase staining.