The very first pregnancy tests looked nothing like the slim plastic sticks you’d recognize today. The earliest known method, dating back roughly 3,500 years to ancient Egypt, involved urinating on bags of grain and waiting to see if the seeds sprouted. From there, pregnancy testing evolved through live animal experiments in the early 1900s before finally arriving at the first home kit in 1976, a clunky contraption of test tubes, eyedroppers, and a small mirror.
Ancient Egypt: Bags of Grain
The oldest recorded pregnancy test comes from an Egyptian papyrus dating to around 1350 BCE. The instructions were simple: a woman urinated into a bag of barley and a bag of wheat, then waited. If the grains sprouted, she was considered pregnant. If they didn’t grow, she wasn’t. Some versions of the test even claimed the type of grain that sprouted first could predict the baby’s sex.
It sounds like folk magic, but a 1963 study found the method had a kernel of truth. Urine from pregnant women did promote seed germination at a higher rate than urine from non-pregnant women or men, likely because of elevated hormone levels. It wasn’t reliable enough for clinical use, but the core idea of testing urine for signs of pregnancy turned out to be on the right track thousands of years before anyone understood why.
The 1920s: Injecting Mice
The first scientifically validated pregnancy test arrived in 1927, developed by two German scientists, Selmar Aschheim and Bernhard Zondek. The test required injecting a woman’s urine into immature female mice, three times a day for three days. Two days after the last injection, the mice were killed and their ovaries examined under magnification. If the woman was pregnant, her urine contained a hormone (what we now call hCG) that forced the young mice into sexual maturity prematurely. A positive result showed ovaries swollen to two or three times their normal size, dotted with small red spots from internal bleeding or tiny yellow spots where new tissue had formed.
The test was remarkably accurate for its time, but it required a laboratory, multiple live animals, trained technicians who could read ovarian tissue, and about five days from start to finish. Each test used five mice. It was expensive and slow, but it was the first method that worked on a reliable, repeatable basis.
The 1930s: “The Rabbit Died”
Within a few years, researchers modified the mouse test to use rabbits instead. This became the Friedman test, and it’s the origin of the phrase “the rabbit died,” which became slang for a positive pregnancy result. The logic was similar: inject a woman’s urine into a female rabbit, then examine the rabbit’s ovaries for changes. Rabbits were useful because they only ovulate when stimulated by a male, so any ovarian changes in an unstimulated rabbit pointed clearly to the hormones in the injected urine.
The rabbit always died, though, regardless of the result. The only way to check the ovaries was to surgically open the animal. A positive pregnancy test and a negative one both ended the same way for the rabbit. The phrase stuck in popular culture for decades.
The 1940s: Live Toads and Faster Results
A major improvement came in the 1940s with the Galli-Mainini test, which used male toads instead of female mammals. A technician injected a woman’s urine under the toad’s skin and then collected the toad’s own urine a few hours later. If the woman was pregnant, the hormones in her urine stimulated the toad’s testes to release sperm cells, which could be spotted under a microscope in a drop of the toad’s urine.
This was a genuine leap forward for two reasons. First, the toad survived. You could reuse the same animal for future tests. Second, results came back in hours rather than days. Laboratories kept colonies of toads on hand specifically for pregnancy testing well into the 1960s.
1976: The First Home Pregnancy Test
The test that most readers are probably picturing arrived in 1976, when the FDA approved a product called e.p.t. (originally “Early Pregnancy Test,” later rebranded as “Error Proof Test”), manufactured by Warner-Chilcott. Three other tests were approved around the same time: Predictor, ACU-TEST, and Answer.
These early kits looked more like a high school chemistry set than anything you’d buy at a pharmacy today. The Predictor kit, whose prototype now sits in the Smithsonian National Museum of American History, contained a test tube, an eyedropper, a small angled mirror, and a vial of chemical solution. To use it, a woman placed a few drops of her urine into the test tube, added the chemical solution, shook the tube, and then set it down on a flat surface for two hours without disturbing it. After waiting, she tilted the kit to look at the mirror built into the bottom. A dark brown ring against a yellow background meant pregnant. If the background stayed completely yellow with no ring, the result was negative.
The whole process demanded patience and a steady hand. Bumping the test tube during the two-hour wait could ruin the result. The instructions were detailed and easy to mess up. Early advertising acknowledged this, and accuracy rates reflected the challenge. False negatives were common, partly because the tests couldn’t detect low levels of hCG and partly because user error was so easy.
How Sensitivity Has Changed
The biggest difference between those 1976 kits and modern tests isn’t just the shape of the packaging. It’s how little hormone they need to detect. The original e.p.t. required hCG concentrations of about 100 mIU/mL or higher in urine to register a positive, which meant the test only worked reliably after a woman had already missed her period by a week or more. At that threshold, it caught roughly 16% of pregnancies or fewer on the day of a missed period.
Today’s most sensitive over-the-counter tests can detect hCG at levels below 6.3 mIU/mL, picking up more than 95% of pregnancies by the day of a missed period. That’s roughly 15 to 20 times more sensitive than the original kits. Other widely available tests detect at 25 mIU/mL, catching about 80% of pregnancies at the same point. The progression from grain bags to toad colonies to two-hour chemistry experiments to a five-minute plastic stick spans about 3,500 years, but the sharpest jump in usability happened in just the last few decades.