#ThrowBackThursday: How Frogs Were Used To Run Pregnancy Test

By Joy Chinecherem

Pregnancy test did not always come in a well-packaged sterile kit, or as easy as just taking a pee on a stick and have your result, in a few minutes.

Less than a century ago, between the 1920s and 1930s, a pregnancy test was like taking a camel through a needle’s eye. It cuts across different gruesome, less accurate, and much slower methods.

Around the 1350 BC, ancient Egyptians sprinkled a woman’s urine on wheat and barley seeds, if it sprouted then it was positive.

There was the Aschheim-Zondek method, also known as the A-Z test; it required injecting the minimum of five mice, rats, or rabbits with a woman’s urine for 3 days, then killing the rodents and examining their ovaries for any enlargement. An estimate of 6,000 test was performed a year. This method not only took time but was considered unfair to the poor animals, serving as sacrificial lambs.

The year 1930 ushered in the use of the African clawed FROG, also known as Xenopus Laevis, and was discovered by British Biologist Lancelot Hogben. Xenopus was discovered in South Africa where Hogben, was teaching and researching about hormones. The African clawed frog is a species of African aquatic frog of the family Pipidae. The species is found throughout much of Sub-Saharan Africa (Nigeria and Sudan to South Africa).

This discovery showed that an Injection of the Xenopus with extracts from an Ox’s pituitary gland made the frogs lay eggs. The urine of pregnant women contained hormones that were made in the pituitary, and that affected the development of ovaries. If those same hormones could trigger egg-laying in Xenopus, perhaps the frog could act as a living pregnancy test.

So in 1937, Hogben and his partner animal geneticist Francis Albert Eley Crew imported 1,500 Xenopus frogs to the UK. Within two years, their team conquered the biggest obstacle of the experiment, raising the frogs in labs and making it easy for doctors to order.

A dose of a pregnant woman’s pee will cause a female Xenopus to lay eggs within 8-12 hours. the test also works on male frogs, which will produce sperm in response to the injection.

The frogs made a great pregnancy test compared to the A-Z for a few reasons.

They required only one injection of a woman’s urine in one animal, whereas the A-Z required two injections a day for three days in up to five rodents. Second, a female Xenopus will lay eggs within hours and won’t need to be sacrificed, and can be reused. Frogs continued to take the fall and had their stomachs bloated with female urine between the 1940s – 1950s.

In the 1960s, scientists developed chemical tests that searched directly for human chorionic gonadotropin (HCG)—the tell-tale hormone that the frogs were reacting to. The frogs were slowly discarded like an old wife.

The African Clawed Frogs was basically the precursor to the pee-on-a-stick home pregnancy test. Today’s pregnancy test strip might be the best thing after sliced bread but the Xenopus was the flour the bread yielded from.