Prior to the invention of immunological pregnancy tests in the 1960s, women relied on the very widespread and popular "frog test" to determine pregnancies. This method was invented around 1930 and required the injection of the patient's blood or urine under the skin of a small living animal, often a frog or a toad—hence the name. If the frog started to spawn within 18 hours (caused by the pregnancy hormone hCG), then the woman was most likely pregnant.
Since the tests had no negative impact on the animal and supposedly caused them no pain, the toad or frog—often kept at pharmacies—could be reused for testing within 14 days. This, by the way, also explains why newspapers of that time disproportionately advertised for frogs and toads.