There were days when rabbits were used for testing pregnancy and even at those time this test was performed to detect the hCG hormones which even modern kits do. It is believed that the scientists from ancient Egypt were the first to discover various pregnancy detecting methods by studying urine.
Although this test was commonly known as rabbit died pregnancy test, however unfortunately rabbit used to die in each and every test irrespective of whether the woman was pregnant or not.
There were rabbit breeding labs where the urine samples were sent for testing. The urine was injected in the rabbit and if the woman was pregnant it would create corpus hemorrhagicum ("bleeding corpus luteum") in the ovaries of rabbit. The corpus hemorrhagicum is a temporary structure that gets formed due to ovulation containing blood that gets clotted quickly. So these rabbits were killed and cut to check for the symptoms of corpus hemorrhagicum in their ovaries.
This rabbit test was the oldest and the most reliable test developed in 1930s by a researcher studying at Pennsylvania University. His research said that if a woman is pregnant then her urine would contain a lot of chorionic gonadotrophin. If this the urine will be injected into a rabbit than due to this hormone jolt the rabbits ovaries would get enlarged and would exhibit noticeable surface changes.
Frog Pregnancy Test
Then there was another test in which Doctors used to perform frog pregnancy tests by using a special species of frogs now known as African clawed frog. How this was performed was that doctors from all over the world used to collect the urine samples from the expecting lady and will ship them to special labs. Here frogs especially female frogs were kept and nurtured in individual tanks.
The lab technicians would inject the urine sample into hind leg of the female frog. After injecting urine inside the frog the frog was put back inside the tank. These tests were performed in evening and the result was captured in the morning. So next day the technicians used to check if in case the female frog has ovulated or if she has given eggs. If the eggs were found that meant the woman was pregnant otherwise not.
It was believed that the hCG hormone which is also known as the pregnancy hormone has catalyzed the ovulation in the female frog. This test was also known as hogben test.
Before these tests even mice and rabbits were used. However tests using mice and rabbits required dissection of these for the examination of ovarian changes and hence they cannot be reused. So this was not considered to be a feasible and profitable business therefore the frog test became famous. Lancelot Hogben was the person who discovered that the test which was being performed on mice and rabbits can also be done on frog and it would be more beneficial as these frogs can be reused.
Frog labs got opened everywhere and thousands of frogs were exported across the world in 1930s. Slowly new test kits were developed and they started replacing these ancient methods. After the invention of over the counter test in 1970s the frog lab slowly got shut down. These frogs were then freed and released into the wild near those labs.
Now the researchers have found that these frogs carry a deadly amphibian fungus which is believed to be responsible for the extinction of approximate 200 species around the world. There are stories as well that these frogs are taking revenge because they were utterly used for these kind of tests.
Thanks to the scientific development that we now have some of the very advanced and sensitive test kits which can test pregnancy very early and hence these poor animals do not have to die due to stupidity of humans.