<Tr> <Th> MedlinePlus </Th> <Td> 003432 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> A pregnancy test attempts to determine whether a woman is pregnant . Markers that indicate are found in urine and blood, and pregnancy tests require sampling one of these substances . The first of these markers to be discovered, human chorionic gonadotropin (hCG), was discovered in 1930 to be produced by the syncytiotrophoblast cells of the fertilised ova (eggs). While hCG is a reliable marker of pregnancy, it cannot be detected until after implantation: this results in false negatives if the test is performed during the very early stages of pregnancy . HCG can be detected via blood 8 days after fertilization of the egg, and in the urine 10 days after . Obstetric ultrasonography may also be used to detect pregnancy . Obstetric ultrasonography was first practiced in the 1960s; the first home test kit for hCG was invented in 1968 . The kits went on the market in the United States and Europe in the mid-1970s . </P> <P> The test for pregnancy which can give the quickest result after fertilisation is a rosette inhibition assay for early pregnancy factor (EPF). EPF can be detected in blood within 48 hours of fertilization . However, testing for EPF is expensive and time - consuming . </P>

When did over the counter pregnancy tests become available