How Were Pregnancy Tests Invented?

by the humans in question with the utmost care. But did you know that from the nineteen thirties to the early nineteen sixties, lab rabbits were key element in human pregnancy tests. It's true, and it's even weirder than it sounds, because it involved injecting those rabbits with human urine. But let's back up a little here. The basic principles behind testing urine for pregnancy date back thousands of years and

continue to this day. Historians believe the physicians of ancient Egypt were the first to discover a method detecting pregnancy through the study of urine. We've talked about this one on the show before. By BC or so, ancient Egyptian women could determine whether they were pregnant by urinating in two different bags, one filled with barley and the other with wheat. If the grain and either bags sprouted, it

meant she was expecting fast forward all the way. In the nineteen sixties, a study found that this is actually accurate about seventy percent of the time because the elevated estrogen levels and a pregnant person's urine can promote seed growth. What wasn't accurate was the attempt to determine the sex of the child based on which sprouted first, Barley for boys, wheat for girls. But still not bad and historians think this marked the beginning of medical urine examination and potentially

laboratory medicine itself. More than three thousand years of urine examination also called eurro scopy or your analysis have followed, with varying accuracy. There was a bit of an expose in the sixty hundreds in London that called out fraudulent physicians using urine to diagnose pregnancy and lots of other conditions. The whistleblower referred to these frauds as piss profits. But urine research continued, and meanwhile, in the late eighteen nineties,

scientists discovered the existence of hormones. A hormone is a product that sells make to regulate specific cellular activities such as cell growth and division, and in the nineteen twenties, scientists pinpointed a specific hormone called human choreonic ganado trop in. It's also called hCG because that's much easier to say. This hormone is found almost exclusively in the blood and urine of pregnant people, though we now know that certain

cancers also produce it in anyone. But intrigued by this hormones linked to pregnancy, a couple of German researchers set out to develop a method of testing for hCG in urine. They decide to exploit the fact that hormones from one animal can generate biological responses in the bodies of other species, sort of like those sprouting seeds. They discovered that by injecting female mice with a pregnant woman's urine, they could stimulate the mice's ovaries and cause them to go into

heat within a few days. They called this test the A Z test. Will note here that just as analyzing urine has a long history and medical science, so too has the use of animals. While often controversial and hopefully replaceable by technology in the future. A number of experiments on animals called bioassays, have led to important breakthroughs in medical science anyway, during the nineteen thirties, researchers applied the

Azy tests methodology to two other species. In South Africa, researchers adapted it for use in frogs, inventing the hogbin test. The frogs would lay eggs if the urine they were

injected with contained hCG. This test was used tens of thousands of times in the nineteen forties through the nineteen sixties, and at the University of Pennsylvania Medical School, one Dr Maurice Friedman made a breakthrough with rabbits similar to mice, If hCG is present in urine injected into female rabbits, the urine stimulates changes to the rabbit's ovaries within just

a few days. The hCG basically fools the rabbit's body into temporarily thinking it's pregnant, and the rabbit's ovaries produced temporary tissue structures that a researcher can spot. The urine injection itself didn't harm the rabbit or the mice or frogs, but unfortunately, the fastest way to check the ovaries of the mammals was to euthanize and dissect the animal. Thousands of rabbits were sacrificed every year, to the point that the rabbit died became a euphemism for saying that someone

was pregnant. The frogs, however, were unharmed and uh reusable. Luckily for the bunnies, though, The first immuno essay that could test directly for hCG and a sample of urine was developed in nineteen sixty. Immuno essays are tests that use specific molecules called antibodies that can bind onto whatever type of particle you're looking for in some detectable way. Maybe it makes the sample clump up, or maybe the antibody is attached to an enzyme that will change the

color of a test strip from white to blue. And yes, today's at home COVID tests are also immuno essays. But it took over a decade to turn this initial discovery into something really usable for pregnancy testing. It involved a lot of research and societal changes, including advancements in prenatal care and the legalization of most abortions at a national level via the Supreme Court's decision in Roe v. Wade in ninety three, both of which incentivized being able to

detect pregnancy as soon as possible. At that time, the best tests available had be sent away to a lab, and we're only reliable for detecting pregnancy at six weeks or later. The first home pregnancy test that's more or less equivalent to the ones we know today was approved for home use in nineteen seventy six and was on store shelves by early night. With the sample of urine, it could display a result within two hours, though it

wasn't as accurate as early as today's tests are. A Modern pregnancy tests still involved detecting hc G, but have gotten more sensitive, meaning they can detect smaller amounts of it sooner in a pregnancy. Okay, a person's body starts producing hCG when a fertilized egg implants itself, hopefully in

the prepared lining of the uterus. See our previous episode on how human conception works for more on that, but basically, under normal circumstances, a person will ovulate about a week after their last period, and if that ovulated egg is fertilized, it'll implant about a week after that. A so that's two weeks into a pregnancy, because pregnancies are calculated from the end of a person's last period, and that's when

the pregnant body starts producing hCG. The presence and or levels of hCG in a person's body can be detected in two ways, via blood test or via urine test. A blood test is a little more accurate, but also more invasive. You have to get blood drawn and often more expensive. You have to go to a medical care provider to get your blood drawn and send the sample

to a lab. But a blood test can detect the presence or quantity of hCG in your blood as early as two to three weeks into a pregnancy, and so before you would have ever missed your period, though it can take a day or more to get the lab results back. A urine test is more common because even though it's a little less accurate, especially early in a pregnancy, it's cheaper, can be done anywhere, and the results are

pretty much immediate. These are done by either collecting a sample of urine and dipping a testing strip into the sample, or by urinating directly on a testing strip. A urine test can generally detect the presence of hCG three to four weeks into a pregnancy, so from slightly before to right after you would have missed your period, and the

results develop on the strip within a few minutes. These tests do very a little, so if you're taking one, just read and follow the instructions, but rest assured that there will be no rabbits, frogs, or barley involved. Today's episode is based on the article how can a Rabbit Tell Me If I'm pregnant? On how stuff works dot com written by Robert Lamb. Brain Stuff It's production of I Heart Radio in partnership with how stuff works dot Com,

and it's produced by Tyler Klang. Four more podcasts from my heart Radio visit the iHeart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.