Lastly: sometimes twin or higher order multiple pregnancies, in which levels of hCG are very high, can cause a false negative pregnancy test. This is called the high-dose hook effect. 4 It's unusual, but possible. if you miss a period and have pregnancy symptoms, see your doctor.
High levels of HCG in early pregnancy prevent antibodies from binding to the hormone, so when a test pack is checked, the results are negative. This condition is known as the prozone effect. So, getting pregnant with twins and having a negative test pack is possible.
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 due to higher levels of hCG.
That said, hCG levels vary from person to person and pregnancy to pregnancy, so hCG levels are not definitive to determine a twin pregnancy. Some people have high hCG levels and only give birth to one baby; others have exceptionally low hCG levels and give birth to multiples.
Confusingly, when levels of hCG are too high, they can also interfere with pregnancy test results. This is why, interestingly, being pregnant with twins can sometimes cause a false-negative pregnancy test.
Yes, it is possible. Getting a negative result doesn't mean you're not pregnant, it may just mean your hCG levels are not high enough for the test to detect the hormone in your urine.
Specifically, twin and multiple pregnancies can have 30% to 50% higher hCG levels than singleton pregnancies at the same point in early pregnancy.
That is, the actual hCG value is higher in a twin pregnancy, but over the course of 24 hours, it will increase by about the same percent as the hCG value in a singleton pregnancy.
Range of hCG levels and what they can mean
The range for singletons is 5 – 397 and for twins it is 48 – 683. As you can see, there is a big overlap between the first hCG level in singleton and twins. What this means is that even if you have a first hCG level of 397, it could be a singleton pregnancy.
You cannot conclusively distinguish a single pregnancy from twins on a urine pregnancy test. That said, you may have a very early positive pregnancy test if you are carrying twins.
You might get a false-negative if you: Take the test too early. The earlier you take a home pregnancy test, the harder it is for the test to find HCG . For the most accurate results, take a home pregnancy test after the first day of a missed period.
Women may get a negative test result on a urine or blood pregnancy test despite being pregnant. Although many factors can contribute to a false-negative pregnancy test, the hook effect occurs when the woman has a high concentration of human chorionic gonadotropin (hCG), the pregnancy hormone.
At high hCG levels in molar pregnancies, a “hook effect” can cause an artificially negative value.
An immediate dark positive result could mean that there's a high concentration of hCG in your urine, and the test is showing an immediate dark result due to the hormone level. One thing to note is that all home pregnancy tests are different and may detect hCG at different levels.
3 WEEKS: Twins implantation
By 3 weeks, each zygote has developed into a ball of several hundred cells, called a blastocyst, and is burrowing into the uterine lining. Because they have different chromosomes, your fraternal twins may or may not be the same gender.
Fraternal Twins: This type of twin set is the most common. This occurs when two different eggs are both fertilized by two different sperm and implant themselves into the uterine wall at the same time.
About one-third of identical twins split soon after fertilisation and form completely separate twins. Like fraternal twins, these twins have separate placentas. The other two-thirds split after they attach to the wall of the womb.
A pregnancy test can find hCG (and give a positive result) in your urine when there is enough in your system. Traces of hCG can be found in your urine from 6 days after the fertilised egg implants in your womb (uterus).
Used incorrectly, used past the use-by date, or even used too early (after missing your period) are all reasons for a false negative. Not enough pee or too much pee can also produce a false negative. Even though the test is 99% accurate, the conditions need to be optimal for it to work to that standard.
An early pregnancy test might pick up very low amounts of hCG. However, it's possible that you don't have enough circulating hCG to get a positive result even on a sensitive test. Another common reason for getting a false negative is not having enough hCG in the urine you test.