The home pregnancy tests only indicate the presence of hCG. We normally, not pregnant, have a range of 50-300 i.u./ml. Hence, left too long in the urine results in a false positive. After implantation, the level of hCG rises dramatically - often doubling every two days - and can reach as high as 30,000 before leveling or, even, declining. It can take more than a week after miscarriage for this level to fall to the normal range. Until the level gets back into the normal range, a home pregnancy test will show a pregnancy.
There are other reasons that the test may be positive. Often miscarriage is incomplete and as long as there is placental tissue present, hCG will be produced, usually at a reduced rate. Some miscarriages do require a d7c to clean up the remnants. It is also possible to abort one twin and the other remains viable and healthy giving a positive reading.
A doctor is more interested in the rate of change of the hCG levels than in the mere presence of hCG. If the level is not increasing at a normal rate (and we do not really know what this is as it varies so much from woman to woman) other problems can be indicated including abnormal growths in the uterus or, at an extreme, ovarian cancer. The only medications that contain hCG are fertility drugs so this is not affected by other drugs, including birth control pills, that you may be taking.
OK, long response with no answer! That is because the home pregnancy tests are binary - yes or no - whilst bodies are analogue - the levels are ever changing. Best guess: if the miscarriage is complete, about a week later the hCG level should not register positive on a home pregnancy test.
The lingering feelings of pregnancy can be a function of the length of the pregnancy. After three weeks the body has not changed much but after nine weeks there wil be changes. The other part of it is psychological. A pregnancy scare stirs all sorts of strange feelings and many of them may become manifest through physical sensations or imagined sensations. Blood levels of hCG are much more telling than urine simply because the blood tests give an analogue result.
Waaaay back in my early twenties, I was three weeks late and then had the nastiest, most miserable period of my life. In retrospect, I certainly was pregnant and miscarried. The only symptom was the missed period. Following the miscarriage, I actually had breast tingles and some morning sickness - after clearly not being pregnant any more. I was also in denial that I had been pregnant and convinced myself that I had some malady that delayed the period. Post-miscarriage, my emotions ran both directions. And, I had no interest in sex until after the next normal period.
Thank god you are asking good questions and not just here wondering where your breasts go when you lie on your back! We have had a run of crap the last several weeks.
Posted: 30 Sep 20:22