One of the earliest ways to detect the possibility of multiples is by monitoring the level of human chorionic gonadotropin (or HCG) in the pregnant person's body.
HCG is a hormone secreted by the liver, colon, and pituitary glands. In pregnancy, the placenta secretes HCG, which regulates the production of other hormones, such as progesterone and estrogen, to maintain the pregnancy. HCG, or the "pregnancy hormone," supports fetal growth and development. It is often injected for people struggling with infertility to increase their chances of getting pregnant.
HCG Screenings to Test for Multiple Pregnancies
In some cases, higher levels of HCG could indicate that a person is pregnant with twins or multiples. However, this is not always the case. Doctors can perform blood tests to screen for HCG levels during the first trimester.
If you're worried about your HCG levels or want to determine the odds you may be carrying twins, HCG monitoring can be useful. But the only way to confirm a pregnant person is carrying multiples is by ultrasound.
Monitoring HCG Levels
HCG levels are first detected by a blood test around 11 days after conception and then by urine test about 12-14 days after conception. Not every individual is a candidate for continuous HCG monitoring. Many people never have their levels evaluated beyond a urine test to confirm pregnancy. However, some doctors recommend testing when there has been conception assistance, a history of miscarriage, or concern for fetal growth.
HCG is the substance detected by common over-the-counter pregnancy tests to determine whether a person is pregnant. These tests measure the amount of HCG in a urine sample to determine whether there is enough of the hormone to indicate pregnancy.
HCG monitoring by blood sample provides a comprehensive picture of the individual's status. A blood sample indicates whether an egg is fertilized and can determine whether the fertilized egg, implanted in the uterus, is developing into an embryo.
It is important to note a single HCG measurement does not tell the full story. If warranted, healthcare providers compare blood samples every few days during the early weeks of pregnancy. With each passing day, increasing amounts of the hormone are detectable in the pregnant person's system. HCG production peaks around 10 weeks at the end of the first trimester, so monitoring occurs only in the first few weeks of pregnancy.
The chart below illustrates average HCG ranges during pregnancy in the first trimester. Check your HCG range regularly and learn what your hormones may mean for your chances of carrying a single baby (singleton), twins, or other multiple pregnancies.
FamilyEducation's HCG Chart to Test for Multiple Pregnancies
|
HCG Levels in Single and Twin Pregnancy |
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|
Days from LMP* |
HCG Range** for Singleton Pregnancy |
HCG Range for Multiple Pregnancy |
|
28 |
9.4-120 |
9.5-120 |
|
33 |
300-600 |
200-1,800 |
|
36 |
1,200-1,800 |
2,400-36,000 |
|
40 |
2,400-4,800 |
8,700-108,000 |
|
45 |
12,000-60,000 |
72,000-180,000 |
|
70 |
96,000-144,000 |
348,000-480,000 |
| *LMP is the date of the start of the last menstrual period. **HCG is measured in mIU/mL |
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As the chart illustrates, HCG measurements are quite inflated when multiple pregnancies occur. However, an HCG level alone is not a reliable indicator of twins or other multiples. In most cases, a high HCG reading will only prompt further investigation.
While HCG levels are higher in instances of multiple pregnancies, abnormally high levels of HCG could indicate medical issues or genetic complications. Consult your doctor regularly and inquire about any changes in HCG to test for conditions such as cancer or potential congenital disabilities.