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Pregnancy Tests
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German Inventors and Researchers > Pregnancy Tests

German Vocabulary: Why do Americans say “rabbit test” and Germans say “frog test” for the outmoded pregnancy test once done only by doctors?

Actually, Germans do also say Kaninchentest (rabbit test) in addition to Krötentest (toad test) or Froschtest (frog test), but an examination of the story behind these terms reveals some interesting facts.

Since the very first scientific pregnancy test was introduced in 1928, several kinds of animals have been used for testing to determine if a woman is pregnant or not. The Aschheim-Zondek test used mice. A later variation of that test (the Friedman test) used rabbits. The Hogben test used a specific species of African toad (Xenopus laevis). Other pregnancy tests were conducted with several varieties of rats. All of these pregnancy tests were based on detecting a female hormone. All of them, with the exception of the Xenopus test, resulted in the death of the test animal ("the rabbit died").

In 1903 the German gynecologist Ludwig Fraenkel (1870-1951) identified the connection between certain homones and pregnancy. He named the hormone that promoted gestation "progesterone." In the 1920s scientists identified a specific hormone, now known as human chorionic gonadotropin (hCG), that is found only in pregnant women. All pregnancy tests, including the modern home-testing versions, are based on detecting hCG (or the results of hCG).

Some of the procedures outlined below may sound a bit grim. It is good to know that pregnancy tests involving killing animals were replaced by non-lethal methods in the 1960s. Here's a brief chronology of pregnancy testing.

A Pregnancy Test Timeline

1928 - Aschheim-Zondek: Also known as the A-Z Test, this very first scientific pregnancy test was developed in Germany. It involved several subcutaneous injections of varying amounts of a woman's urine into the backs of immature female mice weighing between five and eight grams. One hundred hours after the first injection, the mice were killed and the ovaries were examined. The A-Z test is named for German researchers Selmar Aschheim (1878-1965) and Bernhard Zondek (1891-1966). Zondek was the first person to describe the ovarian hormone and earned worldwide renown for discovering gonadotropins. He and Aschheim both worked at Charité Hospital's Women's Clinic in Berlin (now the Institute of Experimental Endocrinology, CCM).

1931 - Friedman: A refined version of the Aschheim-Zondek test, the Friedman test used rabbits instead of mice. Its advantages were the availability of the animals, a reduced error rate, and the reduced time required for completion of the test. The subject's urine was injected into the ear vein of a female rabbit. The test, named for Maurice H. Friedman (1903-1991), could be read within 36 to 48 hours after injecting the urine.

1939 - Hogben (Xenopus): In the Hogben test, a female African clawed toad (Xenopus laevis) is injected with urine (or an extract) into the dorsal lymph sac. The presence of five, six, or more eggs within four to twelve hours indicates pregnancy. A similar test was done using male frogs or male toads. A woman's urine or serum is injected into the dorsal lymph sac of two male frogs (Rana pipiens) or male toads (Bufo marinus). The presence of spermatozoa in the cloacal fluid of both animals is positive; in one animal, inconclusive; in neither animal, negative. This test is named for the British biologist Lancelot Hogben (1895-1975). Although the Hogben pregnancy test had the advantage of not killing the test animals, it was replaced by immunological methods in the 1960s.

1960 - Hemagglutination inhibition test: Also known as the Wide-Gemzell test, this was the first pregnancy test that did not require an animal. It tested urine for certain reactions with purified hCG. Much faster and cheaper than previous tests, it was, however, not as accurate.

1970 - Wampole test: This was a two-hour test kit available to physicians. It still required test tubes, syringes, and other items making it unsuitable for home use.

1976 - ACU, Answer, e.p.t. and Predictor: These home pregnancy test kits received FDA approval in 1976. Warner-Chilcott's e.p.t. test would be the first on the market at the end of 1977. It sold for about $10, but still required two hours for results. It was more accurate for positive results than negative. Current versions are more reliable.

1990s - Enzyme testing: Continuing research leads to better accuracy and improved methods. A large variety of home tests exist today, all based on an increase in urinary levels of hCG after fertilization. But no animals are harmed any longer—neither rabbits nor toads!

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Also see: The Rabbit Died by About's Pregnancy Guide.


Related Trivia

  • In 1827 the Prussian-Estonian naturalist and embryologist Karl Ernst von Baer (Karl Maksimovich, 1792-1876) discovered the mammalian ovum (female egg).
  • Another German at Berlin's Charité Hospital was bacteriologist August Paul von Wassermann (1866-1925), who developed the "Wassermann" test, the first reliable test for detecting syphilis, in 1906.
  • In 1934 German chemist Adolf Butenandt (1903-1995) isolated the female hormone progesterone. For this discovery and his other work with sex hormones he won the 1939 Nobel prize in chemistry (along with Leopold Stephen Ruzicka). His work helped lead the way to large-scale production of cortisone.
  • There is a movie named Rabbit Test (1978). It stars Billy Crystal and Joan Rivers. Lionel Carpenter (Crystal) becomes the world's first pregnant man.

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