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But why did a pregnant woman's urine kill the rabbits? Actually, it didn't; the rabbits were simply euthanized after they had been inoculated and their ovaries examined. Through trial and error, researchers later found that it wasn't necessary to kill the rabbit at all, and one rabbit was used for several tests, after allowing the ovaries to regress after a positive result. Eventually, more sophisticated tests were developed that didn't use animals at all. But even today's modern laboratories and home pregnancy kits measure the same hormone levels as the tests carried out in the 1920s.