Human chorionic gonadotrophin hormone (hCG), is unique to pregnancy.It is the hormone detected in blood and urine. Tests for hCG are extremely sensitive, and only the smallest concentration of hCG can lead to a pregnancy diagnosis. In a twin pregnancy there are elevated levels of hCG, making it possible to have a very early positive result. However, home pregnancy tests won’t confirm if twins are present, only the presence of hCG.
It takes around 2 weeks after conception for hCG to be detected in a hCG pregnancy test. Low levels of hCG may be detected in a woman’s blood 8 to 11 days after conception. Sometimes with multiples, there is a higher, early trend in hCG levels. Twin and multiple pregnancies may also have 30 to 50% higher hCG levels than for one baby.
Measuring hCG levels for twins cannot confirm the presence of twins. It’s only when twins are seen on ultrasound that they can be accurately diagnosed.
Twin pregnancy hCG levels
When a mother is carrying a twin pregnancy, she generally has higher hCG levels than a woman who is pregnant with one baby. But this is not a guarantee as hCG levels vary between individual women. What might be considered high in one woman can be within a normal range for another.
hCG levels tend to peak towards the end of the first trimester, before gradually declining over the rest of the pregnancy. hCG levels can also vary at different times of the day and from week to week. Remember, it is the pattern of hCG measurements which is important, not one single result.
How do I know what my hCG levels should be?
The average blood levels of hCG during pregnancy are:
Borderline pregnancy result: 10 tp 25 U/L
Positive pregnancy test: more than 25 U/L
The only way to know what your hCG levels are for sure is by having blood tests which measure hCG, specifically hCG levels for twins. Women who are undergoing fertility assistance and having regular blood tests may have specific insights into the hCG levels.
What is important is not so much the individual readings and concentration of hCG but a measurable increase over time. This is a sign that the placenta is secreting sufficient hCG to maintain the developing embryo.
My hCG level is high—does that mean I’m having twins?
No, not necessarily. There are many reasons for a high reading, and remember, there is a wide range of normal when it comes to hCG levels. These levels should not be used to estimate pregnancy gestation either, as they can vary widely.
Even if you are pregnant with twins, there’s no guarantee you will produce hCG any sooner than if you were pregnant with one baby. But because your levels may be higher, it is possible to detect a pregnancy slightly earlier.
Why would I have low hCG levels?
Consistently low levels of hCG and an absence of other pregnancy symptoms may indicate pregnancy complications. An ectopic (tubal) pregnancy, a blighted ovum or a non-viable pregnancy may be present. Sometimes, low levels of hCG are detected when there has been a mistake calculating the length of the pregnancy.
Why would I have high levels of hCG?
If the level of hCG is very high, this may be because of a multiples pregnancy, miscalculation of dates, a molar pregnancy or placental tumor. Speak with your healthcare practitioner if you’re concerned.
Frequently asked questions about hCG
How much higher are hCG levels for twins?
For women having a multiples pregnancy, it is common for hCG levels to be 30 to 50% higher than those with a singleton pregnancy. But this elevation is not evident until after the first period is missed.
I’m taking medication, can this affect my pregnancy test?
Some medications including anti-convulsants for epilepsy, fertility drugs and diuretics including tranquillizers can affect results.