The Evolution of Pregnancy Tests

The earliest pregnancy test to be recorded was in use around 1350 BC, when Egyptian women were instructed to urinate on wheat and barley seeds. If the barley sprouted, they were likely pregnant with a boy; if the wheat sprouted, a girl. And if nothing sprouted, they weren't pregnant. (As outlandish as it sounds, one 1963 study found this method correctly predicted gender about 80 percent of the time.)

By the Middle Ages, women had transitioned from peeing on seeds to peeing in containers to be assessed by physicians, who looked for visible cues including granules, turbidity and color changes. These physicians specialized in the analysis of urine and were known as "piss prophets," who diagnosed a variety of medical conditions, including pregnancy. (Today, it's hypothesized that piss prophets were actually just attuned to a variety of more telling symptoms presented by the patient.)

In the 1890s, scientists became aware of hormones and started seriously studying how these chemicals impact and align with certain medical conditions. But they were still figuring out which hormones did what, and how to measure them. This would eventually prove pivotal. But at this time, women were still waiting for more obvious signs of pregnancy, like the continued absence of their period, morning sickness and weight gain.

It was also around this time doctors started encouraging women to make an appointment as soon as they suspected pregnancy. Even though there wasn't a reliable test yet, this focus on prenatal care had a positive impact on the health of infants.

We have mice to thank for the discovery of the first scientific pregnancy test. In 1927, when the study of hormones was gaining momentum, German scientists S. Aschheim and Bernhard Zondek found that when injected with the urine of a pregnant woman, immature female mice would begin to ovulate.

This was revolutionary—but complicated. In order for this method to accurately detect pregnancy, a woman had to wait until two weeks after her missed period, then five mice would be injected with her urine. The mice would have to be killed and dissected to determine whether ovulation had occurred, and the results took about a week.

At this time, "I killed the mouse" became a popular, tongue-in-cheek way to announce a pregnancy. The mouse-killing test was named "A-Z" after the scientists who discovered it.

It was an unfortunate time for lab mice, but the pregnancy hormone had been uncovered! In this very crude version of a pregnancy test, Aschheim and Zondek had isolated human chorionic gonadotropin (hCG), the hormone produced when a fertilized egg is developing into an embryo—which is the same hormone we look for with today's pregnancy tests.

After mice came rabbits and frogs. Rabbits were easier than mice to inject with the urine, but frogs provided the shortest waiting time, as hCG could be found in their eggs, saving the frogs from dissection.

It wasn't until 1972 that scientists discovered a way to skip the mouse sacrifice and identify hCG in a woman's urine at the doctor's office. But there was still that pesky waiting period.

"Oftentimes, when you want to be pregnant, you want to be pregnant yesterday," said Jennifer Conti, M.D., OB-GYN, an advisor for Modern Fertility, the maker of at-home pregnancy tests and other fertility products.

In the 1970s, women were still anxiously awaiting those doctor's appointments. The sexual revolution was underway, but doctors weren't always the most progressive when it came to sexual freedom. So, going to a doctor about pregnancy could be intimidating—particularly for single or younger women who might be walking into an uncomfortable lecture. For that and many other reasons, it was a big deal when women could finally take pregnancy tests in the privacy of their home.

You might assume it was a scientist who figured out a way for women to test at home, but Margaret M. Crane was a product designer. The 26-year-old worked for Organon Pharmaceuticals, designing containers for creams and ointments.

Her lab was one that received urine samples from doctors testing for pregnancy, analyzed the results, and sent them back for the doctor to deliver to patients. But Crane wondered, why not skip the lab and design a way for women to perform this relatively simple test at home?

Abortions were still illegal in most states, and gender discrimination was rampant in the workspace. Crane understood the significance of allowing women to obtain this information about their bodies on their own.

Crane tinkered away at her own prototype—the very first version of the at-home pregnancy test. Eventually, she had developed a system including a test tube, a mirror and a compound that would turn red if the urine added to the tube contained hCG. Her bosses weren't interested. They worried about cutting doctors out of the equation.

Crane went on to sell the rights for $1, and the first at-home pregnancy test didn't go to market until 10 years after Crane's invention.

When the at-home pregnancy test finally hit pharmacy shelves, it looked much like Crane's prototype, including a vial and an eyedropper. The test was called "E.P.T." for "early pregnancy test". It cost $10 and took two hours to deliver results, which were 97 percent accurate for positive results. Advertisements called it "a private little revolution."

Thankfully, at-home pregnancy tests no longer look like something you might find in a high school science class.

The "stick test" available for at-home use today, with its compact shape and absorbent end for urine, first came out in 1988. Modern pregnancy tests are convenient and reliable—and they still work by detecting the presence of hCG in urine.

At-home pregnancy tests are most accurate after you've missed your period. But early detection tests now allow you to test up to six days before your missed period—with slightly less accurate results.

The timing of the production of hCG depends on a variety of factors, and it's possible to test too soon and receive a false negative. If you get a negative pregnancy test before your missed period, the clinical recommendation is to test again in a few days.

False positives, on the other hand, are extremely rare, but certain medications containing hCG or a recent miscarriage can cause this.

It's natural that women are often still anxious to confirm their results at a doctor's office. Conti encourages women to go ahead and call the clinic as soon as they get a positive at-home pregnancy test. This isn't so important for confirmation.

"The at-home tests are incredibly reliable," she said. But it's important to get in for that first consultation and set yourself up for the best prenatal care.

Conti confirmed the ability to test early and at home is helpful in the fertility journey. If you're not pregnant and bleeding occurs, but you haven't taken a test yet, "it might not be clear whether it's an early miscarriage or your regular period that came a bit late." That knowledge of a potential miscarriage is important information to know and give your doctor.

When at-home pregnancy tests were first introduced, doctors worried that women "couldn't handle" the information they were obtaining without the presence of a doctor—"Often a white male doctor," Conti added.

She pointed out that while medicine has moved past this demeaning concern—women, after all, have been handling the knowledge of pregnancy since the beginning of time just fine—a similar narrative is now happening with regard to at-home fertility tests.

"We've seen a similar response of, 'Well, you don't know if people can handle this information.'" But Conti believes that just as at-home pregnancy tests provide women with the power and privacy to obtain pertinent information about their body at home, additional at-home products, like ovulation and hormone testing, help women feel empowered in their fertility journey.

Knowing you're pregnant (or not) is the first step in an exciting journey. A lot more information is coming your way soon—and doctors will play an important role in helping you prepare for a healthy and safe pregnancy and delivery. But we think finding out at home is pretty great—no mice required!