The Link Between HCG Levels and Miscarriage

Human chorionic gonadotropin hormone (hCG) is a hormone produced by the placenta while expecting. If hCG levels fall or plateau early in the first trimester, doctors may suspect a potential pregnancy loss. Here's everything you need to know about the connection between hCG levels and miscarriage.

Normal hCG Levels in Pregnancy

During the first few weeks of pregnancy, hCG levels usually double every 29-53 hours. They peak about 8-10 weeks after implantation, and then they slow down and level off, according to Dr. Brennan Lang, an OB-GYN at Baylor Obstetrics and Gynecology at Texas Children's Pavilion for Women.

There's a wide range of normal hCG levels, so high or low numbers don't usually cause concern. In fact, up to 25% of healthy pregnancies don't have hormone levels that double every two days, says Michele Hakakha, M.D., an obstetrician and co-author of Expecting 411.

Even so, too-low numbers—or numbers that start dwindling or plateauing—may raise concerns. It's possible that the doctor miscalculated your conception date, and your pregnancy isn't as far along as previously thought. But you could also be suffering from a blighted ovum, ectopic pregnancy, or a miscarriage.

Low hCG Levels and Miscarriage

Your doctor may perform a single hCG test at each prenatal appointment to make sure your first trimester is progressing properly. If hCG levels aren't rising like they should—or if you're experiencing symptoms of miscarriage— your OB-GYN may request that you take two hCG tests about 48 hours apart. Comparing the results will let her see trends in your hCG levels.

HCG levels during miscarriage "usually fall, plateau, or rise abnormally slow," says Dr. Lang. He clarifies a "slow" rise as less than 35% over 48 hours. Any of these trends can signal miscarriage, but most of the time, "you have to wait until a pregnancy can be seen on ultrasound around six weeks to confirm things are going normally," says Maureen Baldwin, M.D., MPH, an assistant professor of Obstetrics and Gynecology at Oregon Health & Science University.

Besides falling or plateauing hCG levels, other signs of miscarriage include:

• Bleeding or spotting
• Cramping
• White-pink vaginal mucus
• Blood clots or tissue coming from the vagina
• Back or abdominal pain

Missed Miscarriage and hVG Levels: Sometimes a miscarriage won't have any symptoms at all. These "missed miscarriages" can be detected through ultrasound and low hCG levels in early pregnancy.

hCG Levels After Miscarriage

After suffering from a miscarriage, your hCG levels will continue to decrease. They should return to normal in about 4-6 weeks, depending on how far along the pregnancy progressed. "After a miscarriage has been completed, there is not typically any need to monitor hCG levels," says Dr. Baldwin. "If a home urine pregnancy test is still positive after a month, or if you still feel pregnant after a week, you should speak with your provider."