Do High HCG Levels Mean You're Having Twins?

In early pregnancy, the placenta produces a hormone called human chorionic gonadotropin (hCG) to support the growth of the fetus. It's called the "pregnancy hormone" because it's only produced during pregnancy, and it's the hormone responsible for making that positive sign show up on your pregnancy test.

During the first few weeks of pregnancy, your hCG levels will rise pretty rapidly as your embryo grows. And you may have heard that hCG levels are higher with twins and higher-order multiples compared to singleton pregnancies. But is that true? The answer isn't clear-cut, but we've broken down what you need to know about hCG levels with twins.

hCG Levels During Pregnancy

While home pregnancy tests can detect the presence of hCG in urine, the only way to know how much hCG your body is producing is through a quantitative blood test like the one your prenatal care provider may order.

HCG levels usually double every 29–53 hours during the first few weeks of pregnancy, according to Brennan Lang, M.D., a board-certified OB-GYN at Baylor Obstetrics and Gynecology at Texas Children's Pavilion for Women. The levels eventually peak around 8 to 10 weeks after implantation, and then plateau as the pregnancy progresses.

Sometimes, health care providers monitor the change in hCG levels to predict the health of a pregnancy. Dr. Lang says hCG usually reaches 90–100,000 mIU/mL. But when analyzing hCG test results, they pay attention to trends instead of numbers. That's because there's a wide range in what is considered "normal" hCG levels, and as long as hCG rises as expected, the pregnancy is probably healthy.

Decreasing or plateauing hCG levels in early pregnancy could signal a miscarriage, blighted ovum (when an embryo never fully forms), or an ectopic pregnancy. On the other hand, unusually high hCG levels could indicate a molar pregnancy, placental tumor, or pregnancy with multiples. But there are other possible explanations for unexpected hCG numbers. For example, higher- or lower-than-expected hCG levels could also indicate that you're further along or not as far along as you expected in your pregnancy.

Are hCG Levels Higher With Twins?

The short answer? Sometimes. There can be a higher initial hCG trend increase with multiples, says Maureen Baldwin, M.D., MPH, an assistant professor of Obstetrics and Gynecology at Oregon Health and Science University. Specifically, twin and multiple pregnancies can have 30% to 50% higher hCG levels than singleton pregnancies at the same point in early pregnancy.

Even so, detection of high hCG levels alone can't reliably predict twin pregnancies. That's because hCG levels vary greatly between every person and every pregnancy, and there's a wide range of normal levels. Plus, not everyone who is pregnant with more than one embryo will even have increased hCG numbers.

"While your hCG level may be higher than expected or rise faster, we cannot reliably predict whether or not you will have twins until we see them on ultrasound," says Dr. Lang. This initial ultrasound may occur as early as week 6 of pregnancy. Dr. Lang also adds that "sometimes an unrecognized vanishing twin can affect the rise or fall of hCG levels in early pregnancy and confuse the picture of an otherwise normal pregnancy."

The bottom line is that if you're feeling anxious over your hCG numbers, it's important to keep in mind that there can be a lot of variation, every person is different, and implantation is not an exact science, so those numbers can be different than you expect.

As long as your hCG levels continue to rise, higher-than-normal numbers shouldn't affect the health of your pregnancy. Your doctor or midwife may monitor your levels to rule out health problems like molar pregnancy and placental tumors.

If twins or multiples are suspected based on your hCG numbers, use of assistive reproductive technology, or a family history of twins, your provider will most likely order an early ultrasound to check, so you won't have to wait in suspense for too long.