Yep, not even kidding. Back in the 1930s, scientists developed special tests using animal or live tissues to identify a hormone most prominently found in pregnant women. This was known as the A-Z test, after its developers Selmar Aschheim, a German chemist, and Bernhard Zondek, a gynecologist. 

This test was done to identify a hormone, called human chorionic gonadotropin or hCG, that’s found prominently in pregnant women. In this test, a female South African clawed frog was injected with a woman’s pee, and if it laid eggs in the next 8-12 hours, the woman was considered pregnant.

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The test also worked with male African clawed frogs, which produce sperm in the response to the injection.

The A-Z test started with the developers injecting five mice with a woman’s urine over several days, then they’d kill the mice, dissect them, and examine their ovaries—enlarged or congested specimens would signal a pregnancy. 

After a few years, a better test was developed, which used rabbits and was about 98% accurate. This test led to women euphemistically claiming “the rabbit died” when referring to their pregnancy.

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Even today, most modern pregnancy tests involve detecting the presence of hCG in urine to determine pregnancy in a woman.