Home pregnancy tests use a sample of a woman's urine to detect
the presence of a hormone (called human chorionic gonadotropin, or hCG) that is
produced during pregnancy. If the test is positive for the hormone, it usually
means the woman is pregnant.
These tests are available without a
prescription, and their accuracy varies. If used correctly, the best tests can
detect hCG as early as the first day of a missed menstrual period (about 14
days after conception). A first morning urine sample (which has accumulated in
the bladder overnight) provides the most accurate test results.
Sarah Marshall, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics