How many days after conception can pregnancy be detected earliest?

Pregnancy can be detected as early as 7 to 10 days after sexual intercourse. This timeframe mainly depends on the secretion of human chorionic gonadotropin (hCG) following embryo implantation. The fertilized egg begins implantation approximately 6 to 8 days after fertilization, and hCG secretion starts after implantation, with the hormone's levels gradually increasing in the pregnant woman's blood and urine.

However, some sensitive home urine pregnancy test strips may detect the presence of hCG as early as 4–5 days before the expected menstrual cycle, which is an early sign of pregnancy. Nevertheless, results obtained this early may not be reliable and false negatives are common. For more accurate results, it is recommended to perform the test within one week after a missed period or to visit a hospital for a blood test to measure hCG levels.

In addition, there are multiple methods for detecting pregnancy, including blood hCG testing and urine pregnancy tests. Blood hCG testing may detect pregnancy as early as about one week after fertilization, while urine hCG testing, such as using a pregnancy test strip, is generally more accurate around two weeks after fertilization.