How Long Until hCG Falls to Zero After Miscarriage?

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Human chorionic gonadotropin (hCG) is a hormone that the placenta makes during pregnancy. It tends to rise through the early stages of pregnancy, doubling every two to three days during the first four weeks or so of gestation and peaking during weeks eight to 11 of gestation.

If you miscarry, your level of hCG will gradually fall. It will eventually return to a pre-pregnancy level of zero (or it will become so low that it's undetectable during testing).

How Long hCG Takes to Fall to Zero

The exact length of time that it takes for hCG to leave your system after a miscarriage varies. It depends on how high the hCG level was at the time that the pregnancy was lost. In general, a person who had a very early miscarriage is likely to have her hCG return to zero faster than someone whose loss occurred later in the pregnancy.

The average span of time that it takes for hCG to disappear from your system is anywhere from 9 to 35 days, according to the American Association for Clinical Chemistry.

Waiting to Try to Get Pregnant Again

If you want to try to conceive again after a miscarriage, it's important to wait until your hCG level has dropped to either zero or an undetectable level. That signals that your uterine lining is back to normal and can receive a newly fertilized egg. Ask your doctor how long it's best to wait before trying for another child. Many medical professionals recommend waiting six weeks to two months. 

Why is it a problem to try to conceive too soon after a miscarriage? First, pregnancy tests (home urine-based tests, and blood tests) measure hCG levels. If your hCG level is still high from the previous pregnancy, you may get what's called a "false positive" reading from the tests. In other words, a pregnancy test might imply that you're pregnant again—even though you're actually not.

Second, if tests show that your hCG level is dropping (a urine-based pregnancy test won't be able to do this, but a quantitative blood-based test will), a doctor may think that you're miscarrying a second time—even though those numbers may still be referring to your first miscarriage. Finally, it can often take a couple of months to have a complete and normal menstrual cycle after a miscarriage. 

Consult Your Doctor About Your hCG Levels

To be sure that your hCG level has returned to zero following a miscarriage, you may want to ask your doctor for a blood test after the pregnancy loss. A blood test is more sensitive in that it can detect how much hCG might be in your body, not just whether it is present.

If you experienced an ectopic pregnancy (when a fertilized egg implants outside the uterus, such as in the fallopian tubes, and can't survive), you may have to wait even longer before you can attempt to conceive again. An ectopic pregnancy usually requires treatment with drugs or surgery. You may need extra time to recover or for the medications to clear your system. Your doctor can advise you on when it's safe to try to conceive.

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