Pregnancy test
[2] Almost all pregnant women will have a positive urine pregnancy test one week after the first day of a missed menstrual period.
[3] Identified in the early 20th century, human chorionic gonadotropin (hCG) is a glycoprotein hormone that rises quickly in the first few weeks of pregnancy, typically reaching a peak at 8- to 10-weeks gestational age.
[9][10] Qualitative tests (yes/no or positive/negative results) look for the presence of the beta subunit of human chorionic gonadotropin in blood or urine.
Low-sensitivity tests detect hCG levels between 1500 and 2000 mIU/mL and have unique clinical applications, including confirmation of medication abortion success.
When used by consumers, however, the accuracy fell to 75%: the review authors noted that many users misunderstood or failed to follow the instructions included in the kits.
[22] Urine tests can be falsely positive in those that are taking the medications: chlorpromazine, promethazine, phenothiazines, methadone,[19] aspirin, carbamazepine and drugs that cause high urinary pH.
hCG levels rise rapidly in early pregnancy and the chances of false negative test results diminish with time (increasing gestational age).
[25] Menstruation occurs on average 14 days after ovulation, so the likelihood of a false negative is low once a menstrual period is late.
A number of factors may cause an unexpectedly early or late ovulation, even for people with a history of regular menstrual cycles.
The ancient Egyptians watered bags of wheat and barley with the urine of a possibly pregnant woman.
[35] 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.
A later article, independently authored, granted Hogben credit for the principle of using Xenopus to determine gonadotropin levels in a pregnant woman's urine, but not for its usage as a functional pregnancy test.
The product became available in Canada in 1971, and the United States in 1977, after delays caused by concerns over sexual morality and the ability of potentially pregnant women to perform the test and cope with the results without a doctor.
[45] Another home pregnancy testing kit was based on the work of Judith Vaitukaitis and Glenn Braunstein, who developed a sensitive hCG assay at the National Institutes of Health.
[48] 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.
