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Many different hormones work in symphony to prepare your body to welcome a new pregnancy. The hormone hCG (human chorionic gonadotropin) is also called the pregnancy hormone because it is normally made in high levels while you’re pregnant.

In fact, pregnancy tests measure how much hCG you have in your urine. You have only small amounts when you’re not pregnant, but levels increase quickly as pregnancy develops. But what happens when that pregnancy ends?

Up to 20 percent of known pregnancies end in miscarriage. Most people who experience this can go on to have a healthy pregnancy.

Sometimes, when a pregnancy ends suddenly, as in a miscarriage or abortion, hCG levels may take some time to level off. Your body will automatically recalibrate hormones to be ready for another pregnancy. But, sometimes this might take a bit of time.

How long hCG stays in your system afterward depends on what stage of the pregnancy you were in as well as other things. Here’s more on what happens to hCG levels before, during, and after pregnancy.

How much hCG you still have in your system and how long you’ll test positive on a home pregnancy test (HPT) after a miscarriage depends on what stage of pregnancy you were in.

It also depends on the reasons for the miscarriage (if any). Different levels of hCG are made depending on what kind of pregnancy you have and how far along you are.

During pregnancy, hCG is normally made by the placenta. HCG signals the body that you’re pregnant and to keep the lining of the uterus (womb) intact, instead of shedding it like in a period. This triggers the uterus lining to grow and produce other hormones that help keep a pregnancy going.

At around 8 to 11 days after conception, your blood still has low levels of hCG. After this, hCG levels should double every 2 to 3 days for the first 6 weeks of your pregnancy.

Levels of this hormone peak around the end of your first trimester and then go down over the rest of a pregnancy. Here’s what hCG levels (in units per liter) might look like before and during a typical pregnancy:

  • Under 10 U/L: Not pregnant
  • 10 to 25 U/L: Very early pregnancy that might not show up on a pregnancy test
  • Over 25 U/L: Positive pregnancy test
  • 200 to 32,000 U/L: About 5 to 8 weeks pregnant
  • 32,000 to 210,000 U/L: Middle to end of the first trimester (about 6 to 12 weeks pregnant)
  • 1,400 to 53,000 U/L: Around the end of the second trimester (25 to 28 weeks pregnant)
  • 940 to 60,000 U/L: During the third trimester (29 to 41 weeks pregnant)

The more babies you are carrying in a pregnancy, the more hCG you’ll produce. The average amount for a singleton baby, according to a 2013 study, is about 502 U/L during the first few weeks of pregnancy. Compare this to the average amounts of hCG for twins (1,093 U/L) and triplets (2,160 U/L) in those first few weeks.

A 2013 medical study that tested 443 women who had miscarriages found that hCG levels declined faster than previously thought. The researchers reported there was a 35 to 50 percent reduction in hCG levels 2 days after, and a 66 to 87 percent reduction 7 days after the pregnancy resolved.

This is a significant drop, but these numbers still mean that you could test positive on an HPT for a week to several weeks after a miscarriage.

Ectopic or molar pregnancy

Medical researchers found that those who had a miscarriage after an ectopic or molar pregnancy had hCG levels that remained higher for a longer time than those who experienced miscarriage for other known reasons.

This might be because of an incomplete miscarriage. This can happen when some of the pregnancy tissue stays in the body a bit longer and keeps making the hCG hormone.

Fertility treatments

If you’re undergoing fertility treatments that include hCG injections, you might have high levels for several days after an injection. Normally, it takes around 10 days for injected hCG to clear from the body, says fertility benefits company Progeny.

New pregnancy

Another reason for higher than normal hCG levels is that you may be pregnant again sooner than you expected.

It’s possible to conceive again very soon after a pregnancy loss or giving birth. Ovulation can happen within 2 weeks after a miscarriage and as early as 45 days after giving birth.

Other causes

Other, less common causes of high hCG levels when you’re not pregnant include certain cancers, such as:

Your hCG levels don’t need to drop to zero before you can try getting pregnant again. They just have to be low enough so that they can’t be detected in a blood or urine test.

Higher levels of hCG can interfere with figuring out when you’re ovulating or give you a false positive on a pregnancy test.

Traditionally, women were advised to wait 6 months after a miscarriage before trying to get pregnant again. However, there is no evidence that it is necessary to wait this long. Most doctors recommend avoiding sex for 2 weeks after a loss to prevent an infection.

You can ovulate and become pregnant as early as 2 weeks after having a miscarriage. It’s up to you to decide whether you are both emotionally and physically ready. If you’ve had more than one miscarriage, your doctor might recommend getting a checkup and genetic testing.

The hormone hCG is made naturally once you’re pregnant to help your growing bud bloom.

The hormone is at its highest levels during the first trimester and then gradually drops off until you deliver your baby. In fertility treatments, hCG is used to stimulate healthy ovulation to help you become pregnant.

Miscarriages aren’t uncommon, especially in first-time pregnancies. Most people can go on to have a healthy pregnancy after experiencing a miscarriage.

If you’ve had a miscarriage you may have some residual hCG left over in your system. How much depends on how far along you were in your pregnancy. It also depends on what kind of pregnancy.

If your pregnancy ended in the first 2 to 4 weeks, you will likely have very low levels of hCG. However, if you had a miscarriage closer to the end of the first trimester (around weeks 6 to 12) you will have more hCG in your blood.

Following a miscarriage, your body will normally balance its hormones — including hCG — in preparation for a new pregnancy. This can happen quickly, but deciding when and if you’re emotionally ready to try again is a personal choice.