The differential diagnosis between early pregnancy, intrauterine or ectopic, and pathologic and physiologic conditions that simulate the gravid state, frequently taxes the resources of the most expert gynecologist. Even advanced pregnancy may be confused with ovarian cysts and uterine fibroids before the fetal skeleton can be demonstrated roentgenologically.
Pulmonary tuberculosis, primary and severe secondary anemias, psychoses, endocrine and metabolic disturbances, and a host of other conditions associated with amenorrhea often mimic the gravid state. Likewise, the abnormal uterine bleeding incident to acute salpingitis is frequently attributed to ectopic gestation. The physiologic amenorrhea of lactation and the early menopause often give our patients great concern. A fairly accurate test to determine the presence or absence of pregnancy is most valuable in these cases.
There are three biologic tests for pregnancy, none of which has been given the "test of time." All of them depend on the effect of either the anterior
MAZER C, HOFFMAN J. THE THREE HORMONE TESTS FOR EARLY PREGNANCYTHEIR CLINICAL EVALUATION: A COMPARATIVE STUDY. JAMA. 1931;96(1):19–23. doi:10.1001/jama.1931.02720270021005