History
Records of attempts at pregnancy testing have been found as far back as the ancient Greek and ancient Egyptian cultures. The ancient Egyptians watered bags of wheat and barley with the urine of a possibly pregnant woman. Germination indicated pregnancy. The type of grain that sprouted was taken as an indicator of the fetus's sex. Hippocrates suggested that a woman who had missed her period should drink a solution of honey in water at bedtime: resulting abdominal distention and cramps would indicate the presence of a pregnancy. Avicenna and many physicians after him in the Middle Ages performed uroscopy, a nonscientific method to evaluate urine.
Selmar Aschheim and Bernhard Zondek introduced testing based on the presence of human chorionic gonadotropin (hCG) in 1928. Early studies of hCG had concluded that it was produced by the pituitary gland. In the 1930s, Georgeanna Joness discovered that hCG was produced not by the pituitary gland, but by the placenta. This discovery was important in relying on hCG as an early marker of pregnancy. In the Aschheim and Zondek test, an infantile female mouse was injected subcutaneously with urine of the person to be tested, and the mouse later was killed and dissected. Presence of ovulation indicated that the urine contained hCG and meant that the person was pregnant. A similar test was developed using immature rabbits. Here, too, killing the animal to check her ovaries was necessary. An improvement arrived with the frog test, introduced by Lancelot Hogben, which still was used in the 1950s and allowed the frog to remain alive and be used repeatedly: a female frog was injected with serum or urine of the patient; if the frog produced eggs within the next 24 hours, the test was positive. This was called the Bufo test, named after the toad genus Bufo, which was originally used for the test. Other species of toads and frogs have been used later on.
Direct measurement of antigens, such as hCG, was made possible with the invention of the radioimmunoassay in 1959. Radioimmunoassays require sophisticated apparatus and special radiation precautions and are expensive. In the 1970s, the discovery of monoclonal antibodies led to the development of the relatively simple and cheap immunoassays, such as agglutination-inhibition-based assays and sandwich ELISA, used in modern home pregnancy tests.
Read more about this topic: Pregnancy Test
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