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As you round out your first trimester, you may start to wonder: What color hair will your little one have? Will they look more like you or your partner? Will they be a fearless daredevil like your sister’s toddler?

While these things will remain a mystery for a while, your OB-GYN may offer you certain tests or screenings to learn more about your growing baby, including their sex.

One diagnostic tool is called the double marker test, which involves giving blood to be analyzed for markers of certain chromosomal abnormalities.

Here’s more about how and when the test is performed, what it screens for, and what you can expect when you receive the results.

Related: Prenatal screening tests

The double marker test, also known as maternal serum screening, is part of a more comprehensive screening called the first trimester screening. It’s not a definitive test. Instead, it’s classified as a predictive test, which means its results report the likelihood of chromosomal abnormalities.

Specifically, this test screens for blood levels of both free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A).

In a typical pregnancy, there will be either 22 pairs of XX chromosomes in female fetuses or 22 pairs of XY chromosomes in male fetuses.

A trisomy is a chromosomal condition in which there are extra chromosomes, such as the following:

  • Down syndrome. This common trisomy is also referred to as trisomy 21 because there’s an extra copy of chromosome 21.
  • Trisomy 18 and trisomy 13. These common chromosomal abnormalities involve an extra copy of chromosome 18 (Edward’s syndrome) or chromosome 13 (Patau’s syndrome).

Levels of hCG and PAPP-A may be either higher or lower than “normal” in pregnancies with these chromosomal abnormalities.

However, blood levels alone don’t produce your results. Instead, the blood test is used along with an ultrasound called a nuchal translucency (NT) scan, which examines the clear tissue at the back of your baby’s neck.

The first trimester screening — double marker test and NT scan — isn’t mandatory. That said, the screening (and others like the cell-free DNA test) is recommended if you’re over the age of 35 or may have an elevated risk of chromosomal issues, such as if you have a family history of certain conditions.

It’s important to remember that the result only tells you whether there’s an increased risk of trisomies. It doesn’t definitively determine whether your baby has any abnormalities.

Before deciding whether you want a double marker test, you might ask yourself what the results would mean to you in the long run.

  • Would knowing about possible abnormalities ease or worsen your anxiety?
  • Would you want to go for more invasive testing if you receive a result that indicates heightened risk?
  • Would the results change how you’d manage your pregnancy?

It’s all about personal choice and your own health history, so there’s really no right or wrong answers to your questions.

There’s a relatively slim time window during which the double marker test can be performed. Your healthcare provider will have you make an appointment for sometime near the end of your first trimester or possibly very early in the second trimester.

More specifically, you’ll have your blood drawn sometime between weeks 11 and 14.

What you pay for the double marker test will depend on your insurance coverage and location. While the test is optional, it may be covered under your health insurance policy.

Call your insurance provider to find out your coverage and whether you need pre-authorization. Alternatively, if you don’t have insurance, you may call your hospital or lab to find out the cost and potential payment plans or rebates.

This test is most often done in conjunction with the NT scan, so you’ll need to pay for both tests for the complete first trimester screening.

The double marker test is a simple blood test. Your doctor will write an order for you to take to a lab. It’s a non-fasting test, so you may eat or drink normally before your appointment unless you’re instructed otherwise.

Labs vary when it comes to turnaround time. In general, you can expect to receive your results within about 3 days to a week. You may want to ask whether your clinic will call you, or if you should call to get your results.

You’ll receive a low-, moderate-, or high-risk result.

Low-risk (“screen-negative”) is considered a “normal” result and means that there’s a low probability of your baby having chromosomal abnormalities.

If your result is in the normal range, you’ll only be recommended for further testing if there’s some other indicator (like family history, age, etc.) or if you desire to learn more for some other reason.

Still, a low-risk result doesn’t always mean your baby won’t have an issue. And it’s important to note that the first trimester screening only looks at markers for Down syndrome, trisomy 13, and trisomy 18 — not other conditions.

If your screening comes back as moderate- or high-risk (“screen-positive”) for abnormalities, you may choose to go over your result with a genetic counselor to learn more.

Your result can be confirmed with more definitive and sometimes more invasive tests, such as noninvasive prenatal testing (NIPT), amniocentesis, or chorionic villous sampling. While some of these tests carry some risk to your pregnancy, they provide a definitive result.

Since the double marker test is done early on in your pregnancy, the information gives you time to make important decisions about further testing, medical treatments, and the overall management of your pregnancy and delivery.

Knowing your risk may also help you prepare for the potential you’ll have a child with special needs and allow you to find the support you’ll need.

Related: What is an amniocentesis procedure?

There are no risks associated with the double marker test. It’s a routine, noninvasive blood test. Of course, be sure to follow your doctor’s instructions and contact your provider with any concerns you may have.

For the most accurate results, the double marker test (blood test) and NT scan (ultrasound) are used together in the first trimester screening. The information gathered from both tests is what gives the result of a low-, moderate-, or high-risk of abnormalities.

When performed without the double marker test, the NT scan is less effective at detecting potential abnormalities.

The NT scan allows your healthcare provider to use sound waves to collect a real-time image of your baby. It’s performed around the same time as your double marker test.

At that point in pregnancy — late in the first trimester — your healthcare provider can measure the size of the clear area on the back of your baby’s neck. Your doctor will also assess the development of the nasal bone, which may be another indicator of a trisomy.

These measurements are combined with your blood results and age-related risk. They’re all calculated together to produce your baby’s potential risk of Down syndrome, trisomy 13, or trisomy 18.

To test or not to test? If you don’t know what to do, start by weighing the advantages and disadvantages of the double marker test and first trimester screening. Ask yourself how knowing this information might help inform your decision to get further testing, as well as the management of your pregnancy.

Be sure to speak with your healthcare provider about this test and its usefulness in light of your unique circumstances. No matter what you decide, close contact with your healthcare provider is key to a healthy pregnancy.