Pregnancy test

A pregnancy test uses markers in a woman's urine or blood to determine whether she is pregnant.

* Around 1927 it was discovered that if you injected the urine of a pregnant woman into a rabbit, there would be corpora hemorrhagica in the ovaries of the rabbit. These bulging masses on the ovaries could not be seen with out killing the rabbit to inspect the ovaries ... [1]

The phrase "the rabbit died" came to mean that your wife "has a bun in the oven", even though all rabbits used in this test died.

* See pregnancy