HCG Levels – Know Twin Pregnancy Better


It is natural for expecting mothers to be full of questions. Since twin or multiple pregnancies are slightly different from single pregnancies, you may be filled with more questions than usual. How does a twin pregnancy differ from a single pregnancy? This, and the particulars of how HCG plays a role in it are discussed in the article below.

Connection Between HCG and Twins

HCG or Human Chorionic Gonadotropin is a hormone that helps in detecting pregnancy. For a single baby, the HCG level varies from 70 to 750 mIU/ml (i.e., milli international units per milliliter, which is a unit to measure hormones). High HCG levels can be found for twins during the early stages for pregnancy. The normal HCG levels for twins is 30% to 50% higher than in single pregnancy, somewhere around 200 to 1750 mIU/ml.

The level of HCG may double every 2-3 days in early pregnancy. Blood tests give best results when taken 7-8 days after ovulation. Most home tests can detect pregnancy 4 to 5 days before the next expected period.

Role of HCG Level in Twin Pregnancy

The body does not produce HCG; rather, it comes purely from the developing baby. Each developing baby secretes a normal amount of HCG, which is double the normal amount in cases of twins compared to single pregnancy. These hormones work collectively to thicken the lining of the uterus, which supports the baby during pregnancy.

Progesterone is a hormone that stimulates the uterus to prepare for pregnancy. It is produced by the corpus luteum (an endocrine gland within the ovary). The purpose of HCG is to keep progesterone levels in balance until the placenta is developed enough to produce its own progesterone.

When expecting a twin, the HCG level increases dramatically during the first three months of pregnancy compared to single pregnancy, making it faster to detect HCG in blood and urine test. It doubles every 48 to 72 hours.

The negative side of high HCG levels for twins is that it can lead to more morning sickness during early pregnancy, which means more nausea and vomiting.

When is HCG Produced?

HCG is produced in the placenta right after implantation. It can be detected in the blood or urine of the woman during early stages of pregnancy through HCG tests. Since the hormone level may fluctuate before periods, it is best to test after one misses their periods.

Sometimes, high levels of HCG, along with its symptoms, can also mean molar pregnancy where the placenta grows abnormally when the sperm and egg join during fertilisation. The sperm here fertilises with an empty egg leading to growth in placental parts, but no baby is formed. This is known as complete molar pregnancy. The other type is partial molar pregnancy, where the mass of the foetus contains both embryo and abnormal cells that can have severe birth defects. The healthy embryo, in this case, will end up being consumed by the abnormal mass.

Elevated levels of HCG can also occur due to gestational trophoblastic tumor, which is a rare form of cancer. If early treatment is provided, then it is highly curable. Another reason for high levels can be ectopic pregnancy where embryo grows outside the uterus, i.e., in the fallopian tube. It must be treated immediately since the fallopian tubes are not designed to hold a growing embryo.

HCG is often injected in the system for women facing infertility to increase the levels of this hormone and increase the chances of pregnancy.

hcg injection

Why is the HCG Level Test Performed?

HCG level test is performed for multiple reasons:

  • Most commonly performed to confirm pregnancy
  • To identify and later diagnose any abnormality in the pregnancy such as ectopic pregnancy, where the uterus develops in the fallopian tube
  • To diagnose potential miscarriage
  • To identify the low levels of the protein PAPP-A in the blood which increases the chances of the foetus having Down Syndrome

 Does HCG Level Test Cause Pain?

There are two types of test to identify HCG level in the system – urine test and blood test. Except for the pinching sensation of the needle during the blood test, there is no other pain involved in any of these tests. In cases where the individual cannot determine the date of ovulation, it is best to perform either of these tests 10 days after a missed menstrual period.

A urine test or home tests are 97% accurate provided they are performed correctly. Here, a test sensitive to HCG level is exposed to the woman’s urine either directly or through a cup containing urine. If the strip changes color, then it means the test result is positive.

A qualitative blood test is the most reliable and sensitive test for identifying the presence of HCG in the blood. Apart from this, quantitative blood tests can be done to determine the amount of HCG present in the blood and also to identify progesterone levels, monitor pregnancies, or correctly identify and diagnose ectopic pregnancies, cancer, and chances of miscarriage.

People having bleeding disorders can experience problems after blood tests are performed. There can be swelling in the veins after the blood samples are taken. However, these are rare cases, and there are very little chances of having problems due to blood tests.

HCG Level in Single and Twin Pregnancies

HCG levels differ significantly in case of a twin or multiple pregnancies when compared to a single pregnancy. Below is a chart that lists the range of HCG in different pregnancies.

HCG Level Chart for Twins and Single Pregnancy
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 = Last Menstrual Period

How Often Does HCG Multiply?

HCG is first produced when the embryo starts to attach itself to the uterine lining. Implantation occurs on an average between 6-12 days after fertilisation and within 9 days.

As the embryo keeps growing and developing into a foetus, the amount of HCG released keeps increasing rapidly. It doubles approximately after every 2-3 days.

As the pregnancy develops, the increase slows down significantly. HCG takes 72 – 96 hours to develop if it is 1200 – 6000 mIU/ml serum. HCG values above 6000 mIU/ml take four or more days to double. Once the HCG level reaches 1000 – 2000 mIU/ml, a transvaginal ultrasound can be done to see at least the gestational sac. The growth becomes slower once it goes above 6000 mIU/ml.

The HCG growth becomes slower after two to three months, and eventually the HCG level declines and remains consistent for the rest of the duration of pregnancy. Doctors can carefully monitor the development of a pregnancy by quantitative blood tests.

A sonogram can be done after HCG levels reach above 6000 mIU/ml as they provide a clearer depiction of pregnancy.

It is also common to have ultrasound screenings when there is a doubt over HCG levels. This can help in assessing and ascertaining the foetal age and growth since blood HCG levels are prone to variations. A transvaginal scan is very common as it is more accurate than an abdominal scan.

Note: Caution must be exercised if the HCG levels are low as it can be a sign of miscarriage, blighted ovum or ectopic pregnancy. Hence, regular monitoring must be done to diagnose it. It can also be due to miscalculation of pregnancy.

It is possible to have a healthy baby in spite of having low levels of HCG. In such scenarios, the results from an ultrasound after 5 – 6 weeks of gestation are more reliable compared to numbers derived from quantitative HCG tests result.

What Can Affect HCG levels?

HCG levels can be affected due to multiple reasons:

1. Multiple Pregnancies

Each baby inside the mother’s womb releases a normal amount of HCG, which increases the overall HCG level in the body. In cases of twins, triplets or more, commonly experienced by older women, the HCG level can be double or triple compared to the normal level in single pregnancy.

2. Genetic Defect

Extremely high HCG levels can be due to genetic complications during fertilisation. As a result, the baby can have Down syndrome. A molar pregnancy can also occur where the placenta overdevelops into an abnormal mass of cell leading to a mole. This can lead to the death of the baby in the mother’s womb which may or may not be detected.

3. Genetic Complications

Low levels of HCG can be experienced due to genetic complications leading to ectopic pregnancy or miscarriages. Pregnancy can be troubled or terminated as a result.

4. Cancer

Cancer in the uterus, stomach, liver, lungs, pancreas and large intestine can also raise HCG levels.

5. Influencing Factors

Pregnancy tests performed early in pregnancy or later in the day can produce false negative pregnancy results. Best results come when the first urine of the day is tested.

6. Infertility Treatments

Often, HCG is injected to treat infertile women, which again increases the HCG level in the body.

Does High Level of HCG Mean That You Will Have Twins?

The presence of higher quantities of HCG in urine can be a sign of twins or multiple pregnancies, but this may not always be the case. The level of this hormone may vary from woman to woman or across pregnancies.

HCG levels see a lot of variation in twin pregnancies and single pregnancies, and can be an important determinant in recognising a twin pregnancy. However, it is not the sole determinant to indicate that you will be having twins, as an increased HCG level can be the result of several other conditions as well.