After you receive your miscarriage diagnosis, you might be confused if you take another pregnancy test and find that it is still positive. Here's what's going on.
Pregnancy tests work by detecting the pregnancy hormone hCG in your urine. Usually, hCG is not present in the body unless a woman is pregnant, so having it in your urine is pretty conclusive for pregnancy. But after a baby stops growing and a miscarriage occurs, the hCG does not disappear from the woman's body right away. The level of hCG falls back down to zero over a period of days or weeks, depending on how far along the pregnancy was when the miscarriage happened.
The median amount of time for hCG to disappear from the body is 19 days, but this can vary based on how high the hCG was at the time of the miscarriage. It can take just a few days to return to zero, such as with a chemical pregnancy, or well over a month with a later loss. Thus, because pregnancy tests usually detect even very low levels of hCG, taking a pregnancy test in the days or immediate weeks after your miscarriage can still show a positive. You may even continue to feel pregnancy symptoms, even when it's 100% certain that you have miscarried.
However, if it has been more than a couple of weeks since your miscarriage, you should call your doctor if you are still getting a positive pregnancy test. In this situation, your doctor may want to monitor your hCG level with blood tests. If the level does not return to zero within a reasonable time frame, there is a chance that there might still be pregnancy tissue in your uterus and you may need a D & C. If you have been sexually active, it is also possible that you might be pregnant again, but your doctor should be able to tell you for sure one way or the other.
Source:
Lab tests Online, "hCG Test." Aug 2004. Accessed 19 Nov 2008.
