From urinating on various grains and seeing what germinated in Egyptian times to burning ribbons in the 17th Century, pregnancy tests have historically been unreliable. Then the 20th Century came, and it brought science.
In the 1920’s the presence of hCG, a chemical produced by the placenta, was discovered to be a way of telling that someone (presumably a woman) was pregnant. The first tests were created in the same decade, using animals. They worked on the principle of injecting the woman’s urine into the veins of a mouse or rabbit, waiting for at least a day and then removing the ovaries. On examination of the ovaries they could find out what effect the urine had on the ovaries and draw their conclusions. Unfortunately the animals had to be killed to do this; it was reliable, but expensive. Then came a new way, a better way, the ‘Frog Test’.
Lancelot Hogben discovered that the same test could be performed on the female African clawed frog. After being injected, if the frog produced eggs within 24 hours, the woman was pregnant. No killing, and yet the accuracy remained. This saved time, and even meant that frogs could be reused. The ‘Frog Test’ was the world’s first cheap and reliable pregnancy test and became the international standard for decades. At the end of the 1950’s it was finally supplanted by technology, technology which went on to produce the pregnancy tests we all know, but don’t all use.