In 1977 the first home pregnancy tests came into our drugstores. Not the sveltely packaged wands with catchy marketing slogans that we’ve come to know, but more a handheld chemistry set with intricate instructions for a science experiment in your own bathroom.
A home pregnancy test kit in those days consisted of a vial of purified water, an angled mirror, a test tube and red blood cells taken from a sheep!
During the 1960s, a pregnancy test was only available by making an appointment to see your doctor and a two week wait for the results of a urine or blood analysis.
Margaret Crane was a freelance graphic designer at a pharmaceutical company and clearly had a scientific curiosity. Having seen a row of test tubes angled over mirrors in one of the labs, she was interested to hear that the tubes were full of urine and reagents for pregnancy tests. The reagents would cause a reaction that would allow a red ring to be reflected into the mirror. “I was absolutely certain that [a home pregnancy test] would be very useful,” she said, when interviewed later. “A woman should have the right to be the first to know if she was pregnant and not have to wait weeks for an answer.”
Initial reactions from the pharmaceutical company that Crane worked for were not encouraging. Their concern was that they’d lose a sizeable part of their business from doctors. However Organon Vice President went to their parent company, AZKO, in the Netherlands and managed to obtain a budget for marketing and production. Many feared that there was a strong moral dilemma that women did not, in fact, have the right to test themselves for pregnancy and that it could be linked to abortion which in turn would anger many churches against a woman’s right to know whether she was pregnant.
Today’s pregnancy test kits also work in the same way by detecting increasing Human chorionic gonadotropin (hCG) in a pregnant woman’s urine. hCG is a glycoprotein secreted by the placenta shortly after fertilization, usually around 6 days after conception. As conception doesn’t always take place at the same time as intercourse, women are advised to wait to take a pregnancy test till after they have missed their period. Once a woman is pregnant, her hCG levels double approximately every 2 days.
Pregnancy tests bought over the counter are now just as reliable as a test performed at your doctors office. hCG hormone traces can be found in either blood or urine and both have the highest concentration in the morning. Home pregnancy test kits are not affected by antibiotics, the contraceptive pill, medicines, illegal drugs or alcohol. However, fertility treatments can affect the results and can provide a false positive reading.
How Does a Pregnancy Test Work?
Urine is absorbed by the fibres in the test stick that are coated with molecules called capture antibodies. These antibodies specifically attract hCG. Pregnancy test wands usually have 3 layers including the reaction zone, the test zone and the control zone. Each zone has capture antibodies that can activate indicator pigment molecules when they detect hCG.
Throughout time there have been various, less scientific, ways that pregnancies have been predicted. One of the oldest recorded descriptions of a pregnancy test is from Egypt and required the woman involved to urinate on wheat and barley seeds. If the wheat grew the Egyptians believed that the woman would give birth to a girl and a boy if the barley grew. If neither grew, they concluded, the woman wasn’t pregnant.
During the 18th and 19th centuries, some doctors believed you could find visible signs within a urine sample that a woman was pregnant. Around the end of the 19th century, scientists began to experiment with chemicals and the word ‘hormone’ was first used in 1905. By the 1920s human chorionic gonadotropin (hCG) had been identified in high concentrations in pregnant women.
German scientists, Selmar Aschheim and Bernhard Zondek’s test, known as the AZ test, involved injecting a pregnant woman’s urine into a mouse or rat which sent the animal into heat. Sadly, you could only find out if this had actually happened by killing the mouse or rat and dissecting it. Soon the mice and rats had been replaced with rabbits and frogs. But the tests weren’t always that accurate and a woman still needed a doctor to perform the test. It wasn’t until 1972 that Judith Vaitukaitis and Glenn Braunstein, researchers at the National Institutes of Health, were able to identify an immunoassay that was able to recognize the levels of hCG, rather than just its presence.
It may not seem a particularly important piece of scientific equipment but the pregnancy test has come a long way and a great deal of science is used to make accurate predictions.