Two Week Wait (2WW)

Last Updated: April 28, 2020

Definition - What does Two Week Wait (2WW) mean?

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 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)

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. The so-called 2WW is inspired by the approximately 14-day time frame that it generally takes for a home pregnancy test to be able to detect adequate levels of hCG in urine.

For greatest accuracy, it is typically recommended to waiting until the first day of a missed period in order to test and receive an accurate result. This typically means around two weeks post ovulation or intrauterine insemination (IUI) or around 12-14 days post embryo transfer.

The downside of early testing is that it is possible to detect a non-viable chemical pregnancy that would otherwise appear as a late period.

If pregnancy is not achieved, the 2WW will end with the start of a menstrual period.

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