From Rodents to Sticks: The Evolution of Pregnancy Tests

Today I learned that there was a point in our history when animals were used as pregnancy test kit. I'm not surprised that humans are experimenting on animals after all, I did dissect a frog and a pregnant rat in our biology class.

But I am really amazed that animals and amphibians were used to be the bearer of good (or bad to some) news to expecting parents for almost four decades from 1920s to early 1960s.

But first, what is a pregnancy test and how does it work?

Here is the answer from WebMD:

Pregnancy tests are designed to tell if your urine or blood contains a hormone called human chorionic gonadotropin (hCG). This hormone is made right after a fertilized egg attaches to the wall of a woman's uterus.

Today, most of pregnancy test kits requires you to put your urine sample in a stick and wait for a few minutes. Change in color in portion of the stick indicates the presence of hCG which means that you are pregnant.

But almost a century ago, the best available test for pregnancy are female mice, rats, or rabbits, and a gruesome process with less accurate results.

The Aschheim-Zondek or "A-Z" test requires injecting immature mouse or rat with a woman's urine. If the subject was not pregnant, there would be no reaction. In the case of pregnancy, the rat would show an estrous reaction (be in heat) despite its immaturity.

Later methods in the 1930s required killing of the animals (mice, rice and rabbits) to check if they developed enlargement in their ovaries after being injected by fluids from a woman's glands.

Then came the frogs!

Xenopus Laevis or commonly known as African clawed frogs reigned as the best pregnancy tests in the world for 2 decades beginning from 1940s to early 60s.

image from wikipedia

Named after British biologist Lancelot Hogben, the "Hogben Test" began in 1930 when he discovered that Xenopus frogs were sensitive to hormone changes. Like the previous processes, a woman's urine will be injected into the back of a frog, and if the frog laid eggs 12 hours to 24 hours later, some dude is going to be a father.

The frogs proved to be great pregnancy test because of its quick results, practicality, and accuracy. Result is known after hours of injection if the frog lay eggs or not. No frogs will be needlessly sacrificed just to check if they have enlarge ovaries. In fact, a frog can be reused again and again. Most importantly, the test seemed to be nearly 100% accurate.

But no, you can't just go to a pharmacy back then and order your frog test. You need to see a doctor who will order it from the lab.

Oh wait, if you are curious to see how a "positive" test result looked like back then, click here!

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