pregnancy tests are based on the detection of ___ in the urine
Pregnancy test A pregnancy test attempts to determine whether a woman is pregnant. Markers that indicate pregnancy 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:[1] 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.[2] The kits went on the market in the United States and Europe in the mid-1970s.
Embryo In humans, a pregnancy is generally considered to be in the embryonic stage of development between the fifth and the eleventh weeks after fertilization,[1] and is expressed as a fetus from the twelfth week.
Pregnancy test Most chemical tests for pregnancy look for the presence of the beta subunit of human chorionic gonadotropin (hCG) in the blood or urine. hCG can be detected in urine or blood after implantation, which occurs six to twelve days after fertilization.[1] Quantitative blood (serum beta) tests can detect hCG levels as low as 1 mIU/mL, while urine test strips have published detection thresholds of 10 mIU/mL to 100 mIU/mL, depending on the brand.[4] Qualitative blood tests generally have a threshold of 25 mIU/mL, and so are less sensitive than some available home pregnancy tests. Most home pregnancy tests are based on lateral-flow technology.
Pregnancy test While hCG is a reliable marker of pregnancy, it cannot be detected until after implantation;[1] 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.