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October 2019 | Published by RCPA

Issue #096

Toads that can tell if you’re pregnant: History of the pregnancy test

Toads that can tell if you’re pregnant: History of the pregnancy test

Today, the pregnancy test is a straight-forward procedure which can be performed by a nurse or doctor, or it can be done at home with a kit bought from a pharmacy. Here we take a quick look at the interesting history of the pregnancy test and speak with Doctor Lee Price, Pathologist-in-Charge of the Sullivan Nicolaides Pathology Department of Biochemistry to learn more.

“A pregnancy test works by checking a woman's blood or urine for the presence of human chorionic gonadotropin (hCG), which is a hormone made by the placenta. The modes of testing for pregnancy can be dated back hundreds of years, with some methods a lot stranger than others. It wasn’t really until the beginning of the 1920s, when people realised that pregnant women produced something that could be found in the urine, that pregnancy testing methods were revolutionised,” said Dr Price.

The history of the pregnancy test can be dated back as far as the ancient Egyptians when techniques involved mixing urine with various grains to determine if a woman was pregnant. If the grains germinated, this meant a positive result and, depending on which grain germinated, the gender could be identified.

New and varied techniques evolved into the Middle Ages when physicians would analyse a urine sample based on its appearance and would also mix the sample with wine or alcohol in order to determine a result. These methods did not generate much success, and it wasn’t really until around 100 years ago that the first major steps were taken in developing the pregnancy test.

In the 1920s, scientists discovered that there is a specific hormone, now known as hCG, which is only found in pregnant women. This marked the first time a single compound could be used for pregnancy testing purposes, but was not good news for baby rabbits, mice or rats. In order to determine the presence of hCG, a sample of a women’s urine would be injected into the animals – if hCG was present then the animal would go into heat, indicating that the woman was pregnant. It was later found that injections of hCG in rabbits, rats and frogs would cause ovulation. This “rabbit test” was surprisingly considered to be around 98 percent accurate but the tests were expensive, required the sacrifice of several animals, and often took days to get results.

“Due to the similarity between hCG and luteinizing hormone (LH), at this time most bioassays were unable to distinguish between the two except at extraordinarily high levels of hCG. A major breakthrough was reached in 1972 when scientists reported a radioimmunoassay pregnancy test that could distinguish between these two hormones in a woman's urine, therefore making it potentially useful as an early test for pregnancy. Soon after, the pregnancy test could be purchased and used in the privacy of one’s home.

“Further advances have really been quite recent. Up until not long ago, you had to wait up to two-weeks after a missed period before beginning to test for pregnancy. Modern laboratory tests, however, are highly sensitive and can detect pregnancy before missed periods - even as early as eight to ten days after ovulation. In the majority of cases now, we perform a blood test around the time of a missed period or in the first week after, when hCG levels will be increasing rapidly,” said Dr Price.

 

 

 

 


 

 

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