Tests for determining whether a woman is pregnant go back to at least 1350 B.C. An Egyptian papyrus from that period describes a pregnancy test in which a woman would urinate on wheat and barley seeds. If the barley grew, she was pregnant with a boy; if the wheat grew, it was a girl; if neither grew, she was not pregnant. A 1963 test of this method showed that it was not simple divination—70 percent of the time, urine of pregnant women helped the plants grow. Other Egyptian diagnostics included examining a woman’s skin and nipples for unusual pigmentation, and having a woman drink breast milk from a woman who has borne a son—vomiting would confirm a pregnancy.
In the Middle Ages “piss prophets” foretold pregnancy by examining the color of urine—pale lemon with a cloudy surface meant pregnancy. Another test mixed wine with urine, and since alcohol reacts with some proteins the test may have been mildly useful.
Scientists in the 19th century turned to their microscopes for definitive answers, but it was not until the early 1900s that hormones were identified. Researchers found that human chorionic gonadotropin (hCG) hormone was found only in the urine of pregnant women, and they developed assays to identify it. If urine containing hCG was injected into a rabbit, the animal would ovulate within 48 hours. The only way of determining ovulation was to kill the rabbit, hence the term “the rabbit died.” Of course, the rabbit died either way, and so cheaper, more humane tests were developed.
In the 1960s and ’70s scientists came up with immunological pregnancy tests—antibodies in the test would react in a specific way with hCG, if present. These tests were refined for greater accuracy, privacy, and simplicity, and in 1977 the first home pregnancy test kits were sold for about ten dollars.Home pregnancy tests have grown more and more sophisticated and easy to use, as well as faster: Many versions have accurate results within just a few days of conception. Even with home kits, however, most doctors require that their patients have pregnancies confirmed by blood tests, which have very little margin of error.