The two-week wait (TWW or 2WW) refers to the estimated period of time between a pregnancy attempt and the date where it is most likely that a pregnancy test is able to accurately indicate if the attempt was successful or not.
Pregnancy tests work by detecting hCG levels in urine or blood. It typically takes around 7-12 days after fertilization for hCG to be detected in blood, or 12-14 days after fertilization to be detected in urine.
FertilitySmarts explains Two Week Wait (2WW)
Why does it take two weeks to find out if you are pregnant? Human chorionic gonadotropin (hCG) is a hormone that is produced in pregnancy by the placenta that finds it's way into the bloodstream almost immediately after an embryo implants. This is the hormone that home pregnancy tests are able to detect.
It typically takes around 14 days for levels of hCG in urine to build up adequate levels that a home pregnancy test is able to accurately detect.
Can you test earlier? It's recommended that you always follow the instructions on the product that you are using. A downside of early testing is that it is possible to detect a non-viable chemical pregnancy that would otherwise appear as a late period.
For the greatest accuracy, it is typically recommended to wait until the first day of a missed period in order to take a pregnancy test and receive an accurate result. This typically means around two weeks post ovulation or intrauterine insemination (IUI) or around 9-11 days post embryo transfer.
If pregnancy is not achieved, the 2WW will end with the start of a menstrual period.