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Pregnancy testing

Xenopus laevis, the species of frog Hogben used for his pregnancy test.

Xenopus laevis, the species of frog Hogben used for his pregnancy test.

Credits:Wellcome Library, London

Modern pregnancy testing kits are cheap and easy to use. Many claim to be 99% accurate. They sample urine or blood and detect chemical markers associated with pregnancy that are found in these fluids. Older testing methods were often based on superstition and false assumptions. Urine is the common thread linking many of them with test kits of today.

Ancient Egyptian texts describe an early urine-based test in which the woman urinated over a mixture of wheat and barley seeds. A boy was expected should barley grow. If wheat grew it was a girl. No growth meant no pregnancy. Other tests from the Middle Ages onwards tried to detect ‘something different’ in the urine. They looked for changes in its appearance, smell and taste, the way it reacted with other substances, and the colour with which urine-soaked cloth burned. These all claimed to diagnose pregnancy - or the lack of it.

Specific hormones associated with pregnancy were identified in the 20th century, and this led to increasingly refined chemical tests to detect them. Initially these were confined to hospitals and doctor’s surgeries. The first home testing kit was marketed in 1978. It looked for the hormone human chorionic gonadotrophin (hCG) and was a chemistry set compared to today’s kits. The results could take two hours. However, kits were improved and simplified. For many years the appearance of a ‘thin blue line’ indicated positive news. Recent tests have replaced the blue line with a digital screen displaying either ‘pregnant’ or ‘not pregnant’.

Bibliography

S Leavitt, ‘A Private Little Revolution: The Home Pregnancy Test in American Culture’, Bulletin of the History of Medicine, 80/2 (Summer 2006), pp 317-345

C Hanson, A Cultural History of Pregnancy: Pregnancy, Medicine, and Culture (Basingstoke: Palgrave Macmillan, 2004)

Glossary:

Pregnancy

The condition of having a developing unborn embryo or foetus in the body. A human pregnancy is usually of 40 weeks gestation.

Hormone

A substance produced in one part of the body which passes into the bloodstream and is then carried to other (distant) organs or tissues, where it acts to modify their structure or function