If you have missed one or more menstrual periods or have one or more of the early signs of pregnancy, you may wonder whether you are pregnant. Home pregnancy tests, which can be purchased without a prescription and are considered highly accurate, can be the first way women determine if they are pregnant. If a home pregnancy test is positive, a woman should call her health care provider to schedule an appointment.
Home pregnancy tests measure the amount of human chorionic gonadotropin (hCG) in a woman's urine. Small amounts of this hormone are present even before the first missed period, and they increase as pregnancy continues.
NICHD research in the 1970s led to the development of the home pregnancy test. Researchers were studying the role of hCG in tracking the success of a cancer treatment. During this study, researchers discovered that high levels of hCG in the urine were associated with pregnancy. Manufacturers used this research to create home pregnancy tests that detect hCG levels in urine with up to 97% accuracy.