How a Pregnancy Test Works
Pregnancy tests detect the presence of the pregnancy hormone hCG (human chorionic gonadotropin) in the blood or urine. Most of the time, hCG is only in a person’s body during pregnancy, so a test is usually fairly conclusive for pregnancy. There are some rare ovarian tumors that secrete hCG, but these are extremely uncommon. However, after an embryo or fetus stops growing and a miscarriage occurs, the hormone does not disappear from a person’s body right away. The level of hCG gradually decreases, falling back down to zero over a period of days, or even weeks, depending on how far along the pregnancy was when the miscarriage happened. Because today’s 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 result. You may also continue to feel pregnancy symptoms after a miscarriage, even when it is confirmed that you have miscarried.
Time Frame for hCG to Return to Normal
You’ll get a positive pregnancy test after miscarriage until your hCG levels return to normal. It takes an average of 12 to 16 days for hCG to disappear from the body, but this can vary based on how high your hCG level was at the time of your miscarriage. It can take around a week to return to zero with a chemical pregnancy (a very early pregnancy loss) and up to a month, or even more, with a miscarriage that occurs later in pregnancy. After that, a pregnancy test won’t be positive.
Reasons for a Persistent Positive Pregnancy Test
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 (a quantitative hCG). If you continue to have a positive blood pregnancy test, there are a few possibilities to consider.
Pregnant Again
If you have been sexually active and have a positive pregnancy test soon after a miscarriage, it’s also possible that you might be pregnant again. Your doctor will be able to tell you for sure one way or the other, though she may need to follow you with blood hCG tests to know for sure.
Incomplete Miscarriage
With an incomplete miscarriage, there is still pregnancy tissue leftover in your uterus. Unfortunately, it does not mean that your pregnancy is continuing or is viable. You may need a simple surgical procedure called a D&C (dilation and curettage) to remove the retained products of conception, which is usually only small pieces of the placenta. These tissues will probably be reabsorbed (broken down) by your body in time, but surgery can help put a stop to heavy bleeding sooner, as bleeding is a common symptom of an incomplete miscarriage.
Molar Pregnancy
Very rarely, a positive pregnancy test may occur with gestational trophoblastic disease—a term used to describe several conditions (like a molar pregnancy) in which there is an abnormal growth of placental tissue.
When Can I Get Pregnant After a Miscarriage?
In the past, it was thought that getting pregnant within 3 to 6 months of a miscarriage raised the risk of problems ranging from toxemia to stillbirth. However, according to the National Institutes of Health, research does not support waiting that long. In fact, studies suggest that you have a greater chance of getting pregnant if you start trying within 3 months of having a miscarriage—and that your risk of complications is not increased.
A Word From Verywell
Experiencing a miscarriage can be an emotional rollercoaster and the confusion over a persistently positive pregnancy test can add to this already difficult situation. Be assured that it can take a variable amount of time (on average two weeks) for a woman’s hCG level to disappear after a miscarriage. If you feel like something is not right, or you are experiencing heavy or persistent bleeding, worsening pelvic pain, or a fever with your miscarriage, seek medical guidance.
