Whether you’re actively trying for a baby or not, if you suspect you’re pregnant, one of the most convenient ways to get confirmation is by taking an at-home pregnancy test in a safe, comfortable environment.

When the fertilized egg attaches to your uterus, a home pregnancy test can detect an increase in human chorionic gonadotropin (hCG) i.e. the pregnancy hormone. Most at-home pregnancy tests are 98% to 99% accurate.

However, there are some instances where the tests might show a false negative (you get a negative result when in reality, you are pregnant). Days later, your period still hasn’t arrived, and you’re cramping, bloated, and confused — are you or aren’t you pregnant?

When it comes to twins, this situation raises an important question — Does carrying more than one baby impact the accuracy of home pregnancy tests? With twin pregnancies, your hCG levels tend to be much higher than when you are pregnant with one baby. 

Logically, you’d expect the test to be positive even faster. However, this is not always the case; the opposite might result in a false negative. In this blog, we will cover why this happens, what contributes to it, and whether twins are the reason for these misleading results.

How do pregnancy tests work?

Pregnancy tests work by detecting levels of the pregnancy hormone hCG. You could do this at home through a urine test, or by visiting the doctor who will confirm pregnancy through a blood test. HCG appears in blood and urine roughly 10 to 14 days after conception.

With home pregnancy tests, each brand is slightly different from the next, so it’s important to thoroughly read the instructions before taking the test. HCG is produced by the cells that create the placenta, which is why hCG levels increase when you become pregnant.

HCG is released once the egg attaches itself to the uterine lining (10 to 14 days after conception). If you test too early and there are less than 5 milli-international units per milliliter of hCG present, the result will be negative. For the result to be positive, there needs to be at least 25 mIU/ml of hCG present in your urine.

When should you test?

Given that hCG is present 14 days after conception, it’s possible to test after that point if you’ve been trying to conceive and tracking your cycle. However, if you don’t know when conception may have occurred, the best time to take a home pregnancy test would be after your missed period, and the result would likely be more accurate.

There is also an ideal time of day to take home pregnancy tests — first thing in the morning after waking up, as hCG levels would be most concentrated at this time. Later in the day, after you have consumed a lot of liquid in the form of water, tea, or coffee, hCG levels will be diluted, and therefore, you could get a false negative result.

Why false negatives occur in pregnancy tests

If you are pregnant, it is possible to get a negative test result i.e. a false-negative. This can happen if:

• You take the test too early when hCG levels are below 25 mIU/ml.
• Take the test too late in the day when hCG levels are not as concentrated.
• Check the test results too soon. Each pregnancy test lists a time to check the test after you either urinate on it or dip it in urine. If you check the result too early, it may show a false negative.

Twin pregnancies and hCG levels

According to a 2022 study published in Cureus, when hCG levels are extremely elevated such as in multiple gestations, home pregnancy tests can produce a false negative. As we mentioned earlier, home pregnancy tests look for hCG levels of at least 25 mIU/ml.

However, in twin pregnancies, hCG levels can reach up to 500,000 mIU/mL which makes it difficult for home tests to interpret the results which leads to a false negative. This is called the “hook effect”, thankfully, this phenomenon is quite rare.

What to do if you think you’re pregnant but get a negative test result

If you have missed your period and begin to experience early pregnancy symptoms, take a home test again after a few days. However, if the result is still negative, your best recourse is to see your doctor.

It’s likely your doctor will suggest a blood test that can more accurately detect pregnancy even with twins because it shows the exact amount of hCG in your blood.

Conclusion

While it seems surprising, being pregnant with twins can, in rare instances, contribute to a false negative pregnancy test result. However, the most common reasons for a false negative remain early or improper testing.

If you suspect you might be pregnant with multiples, it’s best to consult your healthcare provider after multiple negative test results and a missed period. In any case, by visiting your doctor you’ll receive a definite result and have peace of mind in your exciting pregnancy journey.