The modern pregnancy test, a simple device offering rapid results, represents the culmination of thousands of years of human curiosity and scientific endeavor. The journey from observing changes in urine to detecting a specific placental hormone in minutes was long and complex. This advancement has profoundly affected personal and medical planning by providing timely and private information.
Early Attempts at Detection
People attempted to confirm pregnancy outside of physical symptoms long before modern chemistry. Around 1350 BCE, the ancient Egyptians devised one of the earliest recorded methods: having a woman urinate on wheat and barley seeds over several days. If the seeds sprouted, the woman was considered pregnant. Researchers in the 1960s found this method surprisingly accurate up to 70% of the time. The germinating effect was likely due to elevated estrogen levels in the urine stimulating the seeds’ growth.
Other historical methods were far less reliable. The ancient Greeks and Egyptians suggested inserting an onion into the vagina overnight; if the woman’s breath smelled of onion the next morning, it indicated she was not pregnant. During the Middle Ages, “Piss Prophets” claimed they could diagnose pregnancy by observing the color and characteristics of a woman’s urine. They might mix the urine with wine, which could occasionally produce a reaction with proteins.
Identifying the Key Marker: Human Chorionic Gonadotropin
The scientific foundation for reliable pregnancy testing was established with the discovery of human chorionic gonadotropin (hCG). This protein is produced by trophoblast cells, which surround the developing embryo and form the placenta. The presence of hCG is the biological signal that allows the maternal body to recognize a pregnancy. It starts being secreted before implantation and can be measured in the bloodstream as early as 10 days after ovulation.
The primary function of hCG is to stimulate the corpus luteum to produce progesterone, which is necessary to sustain the early pregnancy. The hormone’s concentration rises rapidly, peaking around the tenth week of gestation. The identification of this specific marker paved the way for accurate laboratory tests.
In the late 1920s, German physicians Selmar Aschheim and Bernhard Zondek made a breakthrough. In 1928, they found that injecting the urine of a pregnant woman into an immature female mouse caused the mouse’s ovaries to enlarge. This reaction indicated the presence of a gonad-stimulating substance in the urine, establishing the first bioassay linking a chemical to the physiological state of pregnancy.
The Era of Biological Testing
The discovery by Aschheim and Zondek led directly to the first reliable, laboratory-based pregnancy test, known as the Aschheim-Zondek (A-Z) test. The procedure involved injecting urine into immature female mice, rats, or rabbits. The animal was injected multiple times over three days, then sacrificed and dissected to examine its ovaries for signs of maturation. Although complex and time-consuming, requiring several days and the sacrifice of the animal, the A-Z test was about 98% accurate and was widely used throughout the 1930s and 1940s.
The phrase “the rabbit died” originated from the use of rabbits in the A-Z test. These animal-based bioassays remained the standard until the 1960s, with several variations developed to improve speed:
- The Hogben Test: Developed by Lancelot Hogben, this test used the African clawed frog (Xenopus laevis). Injecting a pregnant woman’s urine induced the female frog to ovulate and lay eggs within 18 hours.
- The Galli-Mainini Test: Developed in 1947 by Carlos Galli Mainini, this test used a male toad or frog. Injecting pregnant urine caused the animal to release sperm within three hours, offering advantages in speed and cost over the A-Z test.
The Invention of the Home Pregnancy Test
The shift away from live animal testing began in the 1960s with immunological assays, which used antibodies to detect hCG. These early antibody-based tests, such as hemagglutination inhibition and latex agglutination tests, were still conducted in a laboratory setting. They were faster and did not require animals, but they still meant a woman had to visit a doctor and wait days for results.
The concept of a private, at-home test was pioneered by Margaret Crane, a freelance graphic designer at Organon Pharmaceuticals in New Jersey. In 1967, Crane realized the lab’s test-tube procedure was simple enough for consumer use. She created a prototype combining the necessary reagents, a dropper, and a test vial into a compact plastic box.
Despite resistance from those who believed testing should remain exclusively with physicians, Crane persisted. Her prototype used immunological technology and delivered results in about two hours. The first consumer product based on her design, “Predictor,” was test-marketed in Canada in 1971. After gaining U.S. Food and Drug Administration approval, the first widely available home pregnancy test, “e.p.t.” (early pregnancy test), hit the American market in 1977. This invention revolutionized the process, empowering individuals with immediate information.