In the 1930s there was a reliable and accurate way to find out if you were pregnant or not. But you had to kill a rabbit.
It’s not haruspicy, but it’s not far off. Pregnant women have a specific distinctive hormone in their blood and urine. Take that pee and inject it into a rabbit. Wait a couple of days, and the injected hormone will cause the rabbit’s ovaries to expand. Kill the rabbit, dissect it, and you can see whether someone is pregnant.
Similar tests used mice, toads, or frogs. In fact, the latter test (using the Xenopus frog) was so popular that frogs became a hot export item for a couple of decades. All this ended with the birth of modern pregnancy tests, which did not require the slaughter of an animal.