In 1927, Zondek and Aschheim developed the rabbit test. The test consisted of injecting the woman’s urine into a female rabbit. The rabbit was then examined over the next couple days. If the rabbit’s ovaries responded to the female’s urine, then it was determined that hCG was present and the woman was pregnant. The test was a successful innovation and it accurately detected pregnancy. The rabbit test was widely used from the 1930s to 1950s. All rabbits that were used in the program had to be surgically operated on and were killed. It was possible to perform the procedure without killing the rabbits, but it was deemed not worth the trouble and expense. Today, modern science has evolved away from using live animals in pregnancy tests, but the rabbit test was considered a stepping stone during the middle of the 20th century.
A replacement for the rabbit test involved using frogs, specifically the African clawed frog, which, like all frogs, lays eggs instead of getting pregnant, and therefore can yield results without the need to cut the animal open