First Trimester Genetic Testing: NIPT, NT Scans, and What to Expect

First trimester genetic testing helps identify potential chromosomal conditions like Down syndrome, Trisomy 18, and Trisomy 13. The two main tools are Non-Invasive Prenatal Testing (NIPT), a blood test analyzing fetal DNA, and the Nuchal Translucency (NT) scan, an ultrasound measuring fluid at the back of the baby’s neck. These tests are typically done between weeks 10 and 14 and are recommended for all pregnancies, regardless of risk level.

Key points:

• NIPT: High accuracy (~99% for Down syndrome), no risk to the baby, detects common trisomies, and can determine the baby’s sex.
• NT Scan: Assesses physical markers like nuchal fold thickness and nasal bone presence, which may indicate chromosomal or structural issues.
• Both tests are screenings, not diagnoses. High-risk results may require follow-up diagnostic tests like CVS or amniocentesis for confirmation.

Early testing gives families time to plan for potential medical needs and delivery options. Combining NIPT with NT scans or additional blood tests can provide a more complete picture of the baby’s health. Always consult your healthcare provider or a genetic counselor for guidance.

How NIPT Works and What It Screens For

What Is NIPT?

Non-Invasive Prenatal Testing (NIPT) is a simple blood test that examines small fragments of fetal DNA, known as cell-free DNA (cfDNA), found in the mother’s bloodstream. These DNA fragments originate from the placenta and typically mirror the baby’s genetic material. Since the test only requires a blood draw, it poses no risk of miscarriage.

This test can be performed as early as 10 weeks into pregnancy and remains an option throughout the pregnancy. For accurate results, a minimum fetal fraction of 4% is necessary, which is generally achieved by the 10th week. However, factors such as maternal body weight (especially over 250 lbs) can reduce the fetal fraction, potentially leading to inconclusive or "no-call" results. Now, let’s explore what NIPT screens for.

Conditions NIPT Screens For

NIPT focuses on detecting the three most common chromosomal trisomies - conditions caused by having an extra chromosome:

Condition	Also Known As	Detection Rate
Trisomy 21	Down syndrome	~99%
Trisomy 18	Edwards syndrome	~98%
Trisomy 13	Patau syndrome	~91%–96%

In addition to these primary trisomies, many laboratories offer optional expanded panels. These can screen for sex chromosome differences, such as Turner syndrome (Monosomy X), Klinefelter syndrome (XXY), Triple X syndrome, and XYY syndrome. Some panels also test for microdeletions, including 22q11.2 deletion syndrome (DiGeorge syndrome). Another optional feature of NIPT is determining the baby’s sex, which some families find helpful for planning.

"We recommend that cfDNA screening for common aneuploidies (trisomies 21, 18, and 13) be made routinely available to all obstetrical patients." - American College of Obstetricians and Gynecologists (ACOG)

While NIPT provides valuable insights, understanding its accuracy and limitations is key to making informed decisions about further testing.

Accuracy and Limitations of NIPT

NIPT stands out as the most precise screening tool for common trisomies, with a false-positive rate of less than 1% - a significant improvement over traditional serum screening, which has a false-positive rate of about 5%. A low-risk result greatly reduces the likelihood of the screened conditions. However, a high-risk result is not a diagnosis and requires follow-up diagnostic testing. ACOG highlights this distinction:

"Patients with a negative screening test result should be made aware that this substantially decreases their risk of the targeted aneuploidy but does not ensure that the fetus is unaffected."

It’s also important to note what NIPT does not cover. For instance, it cannot detect structural issues like spina bifida or other neural tube defects. These conditions are best identified through an ultrasound or alpha-fetoprotein (AFP) testing. This is why a detailed anatomy ultrasound, typically performed between 18 and 22 weeks, remains a standard part of prenatal care, regardless of NIPT results.

Understanding the NT Scan

What Is the NT Scan?

The Nuchal Translucency (NT) scan is an ultrasound performed between 11 and 14 weeks of pregnancy to assess fetal anatomy. Unlike blood-based tests like NIPT, the NT scan focuses on measuring a fluid-filled space at the back of the fetus's neck called the nuchal fold. Timing is key because this fluid naturally reabsorbs after 14 weeks.

The scan is typically done using an abdominal ultrasound and gel, though a vaginal scan may be needed if the view is unclear. A full bladder can help improve image quality.

"The nuchal translucency test measures the nuchal fold thickness. This is an area of tissue at the back of an unborn baby's neck. Measuring this thickness helps assess the risk for Down syndrome and other genetic problems in the baby." - MedlinePlus Medical Encyclopedia

During the procedure, the sonographer also checks for the presence of the fetal nasal bone. While the absence of a nasal bone can be a soft marker for chromosomal abnormalities, it’s worth noting that some healthy fetuses may not show a visible nasal bone at this stage. The NT scan provides a detailed look at fetal development, complementing the genetic insights offered by NIPT.

What NT Results May Indicate

The NT scan offers critical information about potential risks and helps guide further testing. Generally, an NT measurement of 3 mm or less is considered low risk. Measurements above 3 mm may indicate an increased risk for chromosomal abnormalities, such as Down syndrome, trisomy 13, or trisomy 18. As Johns Hopkins Medicine explains:

"In some pregnancies, when the fetus has Down syndrome, trisomy 13 or trisomy 18, there is extra fluid behind the neck." - Johns Hopkins Medicine

Beyond chromosomal conditions, an enlarged nuchal fold can sometimes signal structural issues like congenital heart defects or skeletal abnormalities - information that blood-based tests like NIPT cannot provide.

If the results suggest a higher risk, healthcare providers often recommend consulting with a genetic counselor. Further diagnostic options, such as Chorionic Villus Sampling (CVS) or amniocentesis, may be discussed. These tests offer over 99% accuracy in confirming or ruling out specific conditions.

NT Scans and Combined First Trimester Screening

The NT scan is even more informative when combined with a maternal blood test in what’s called Combined First Trimester Screening. This approach measures two proteins in the mother’s blood - Pregnancy-Associated Plasma Protein-A (PAPP-A) and beta-human chorionic gonadotropin (beta-hCG) - and factors in the NT measurement and maternal age to estimate risk. If the calculated risk is around 1 in 250 or higher, further diagnostic testing is typically recommended.

Here’s how detection rates compare:

Screening Approach	Down Syndrome Detection Rate
NT Scan Alone	~70%
Combined First Trimester Screening (NT + blood work)	~96%
NT Scan + NIPT	~95%

An NT scan alone identifies about 70% of Down syndrome cases. When paired with blood markers, detection improves significantly to 96%. While an elevated risk result suggests a higher probability of an issue, it’s important to remember that many pregnancies with increased NT measurements result in healthy babies. Next, we’ll look at how to prepare for and navigate your testing experience.

NIPT, NT Scans, and Combined Screening: A Side-by-Side Look

Key Differences Between Screening Methods

Each first-trimester screening option takes a unique approach to assessing risk. NIPT involves a simple maternal blood draw to analyze cell-free DNA (cfDNA) from the placenta. On the other hand, the NT scan is an ultrasound that measures the fluid-filled space at the back of the fetal neck and checks markers like the nasal bone. Combined screening combines an NT ultrasound with a blood test that evaluates PAPP-A and beta-hCG levels to calculate an overall risk estimate. One major distinction is timing: NIPT can be done as early as 10 weeks, while NT scans and combined screenings are typically performed starting at 11 weeks.

Feature	NIPT	NT Scan	Combined Screening
Procedure	Maternal blood draw	Ultrasound	Ultrasound + blood draw
Earliest Timing	10 weeks	11 weeks	11 weeks
Down Syndrome Detection Rate	~99%	~70%	82%–96%
False Positive Rate	<1%	Higher than NIPT	~5%
Structural Defects	Not detected	Can detect	Can detect
Fetal Sex	Yes	No	No

It’s worth noting that NIPT does not identify structural birth defects, such as congenital heart conditions or skeletal issues, which NT scans (and combined screenings) are equipped to detect. These differences highlight the importance of understanding how follow-up testing fits into each method.

Detection Rates and Follow-Up Testing

NIPT stands out for its high sensitivity and low false-positive rate when detecting chromosomal conditions. However, combined screening has the added capability of identifying structural concerns that NIPT cannot address. Another consideration with NIPT is its 3%–4% no-call rate, often caused by low fetal fraction. This can happen with earlier testing or in cases of higher maternal body weight. In contrast, NT scans and combined screenings are not typically affected by such factors.

If any screening indicates a high risk, the next step involves diagnostic testing, such as Chorionic Villus Sampling (CVS) or amniocentesis, which provide confirmation with over 99% accuracy.

"A positive cfDNA result should be followed by genetic counseling, a detailed anatomic survey, and a recommendation for diagnostic testing." - Society for Maternal-Fetal Medicine

How to Choose a Screening Option

Choosing the right screening method depends on your individual priorities and circumstances. If chromosomal accuracy is your main focus, NIPT offers the most reliable results with the fewest false positives. However, because NIPT doesn’t evaluate fetal anatomy, pairing it with a first-trimester ultrasound - whether an NT scan or combined screening - can provide a more complete picture of the baby’s development.

It’s also a good idea to check with your insurance provider about NIPT coverage, as the test can be expensive if not fully covered.

"No one prenatal genetic test is superior in all situations, and clinicians and patients should understand the risks, limitations, and benefits of available testing options." - ARUP Consult

For those with a family history of chromosomal conditions or previous abnormal screenings, consulting a genetic counselor can be invaluable in navigating the options and making an informed decision.

What to Expect Before, During, and After Testing

Preparing for Genetic Testing

Your healthcare provider will guide you through your options based on factors like your age, family history, and how far along you are in your pregnancy. This is also the time when informed consent is obtained. Keep in mind that screening results offer probabilities, not definitive diagnoses. One practical step to take early is checking with your insurance company - NIPT (Non-Invasive Prenatal Testing) can be expensive if it’s not covered.

Both NIPT and NT (Nuchal Translucency) scans are noninvasive, so there’s no need for fasting or special dietary prep. It’s also a good idea to discuss these options with your partner to ensure you have a solid support system. Feeling prepared can make the process smoother, so let’s dive into what happens during the tests.

What Happens During Testing

NIPT involves a simple blood draw to analyze fetal cell-free DNA from the placenta. It’s quick and routine.

The NT scan is a specialized ultrasound that happens between weeks 11 and 14 of pregnancy. During this scan, the technician applies gel to your abdomen to get a clear ultrasound image. They’ll measure the nuchal translucency, which is the fluid at the back of your baby’s neck. Sometimes, a transvaginal ultrasound may be used for a better view. Typically, a measurement of 3 mm or less indicates a lower risk. Plus, you’ll often get to see your baby on the screen during the scan - a special moment for many parents.

Understanding Your Results

Once testing is complete, here’s what to expect regarding your results. NIPT results usually take 1–2 weeks, while NT scan results are available within a week. Results are classified as low-risk, high-risk, or inconclusive (sometimes called "no-call").

• Low-risk results are reassuring but don’t rule out all chromosomal conditions.
• High-risk results indicate an increased likelihood of a condition and call for further testing.
• No-call results happen when there isn’t enough fetal DNA to analyze, which can occur with early testing or certain factors like a higher BMI. Additional evaluation will be needed in these cases.

If you receive a high-risk result, the next steps often include genetic counseling and diagnostic testing, such as chorionic villus sampling (CVS) or amniocentesis. These tests are highly accurate, with over 99% reliability.

"A positive screening result should always be followed by diagnostic testing before any irreversible decisions are made regarding the pregnancy." - StatPearls

It’s worth noting that diagnostic tests do carry a small risk. For example, amniocentesis has a risk of about 1 in 500 to 1 in 1,000, while CVS carries a similar risk of approximately 1 in 500. Genetic counselors can help you navigate these risks and decide on the best path forward based on your unique situation. These follow-up steps align with recommendations from major medical organizations.

Conclusion

First trimester genetic testing provides critical information as early as 10 weeks into pregnancy. NIPT (Non-Invasive Prenatal Testing) boasts detection rates of about 99% for Down syndrome and 98% for Trisomy 18, with a false-positive rate below 1%. Similarly, combined first trimester screening - a combination of an NT scan and blood work - achieves detection rates of up to 96% for Down syndrome. These screenings enable early and informed decision-making, paving the way for timely care and intervention.

It’s important to note that these tests are screenings, not definitive diagnoses. As ACOG emphasizes, a high-risk result signals an increased likelihood, not a certainty, of a condition.

Planning for postnatal care is just as essential. Early results allow time to consult with genetic counselors, pursue diagnostic testing if necessary, and consider all available options to support your child’s health from day one.

One such option is newborn stem cell banking. Cord blood has already been used to treat over 80 conditions, including leukemia and sickle cell disease. Additionally, research into cord and placental tissue shows promise for conditions like autism and cerebral palsy. Since collection can only happen at birth, this decision must be made before delivery. Americord Registry provides banking plans for cord blood, cord tissue, and placental tissue, backed by AABB accreditation and their proprietary CryoMaxx™ processing to ensure quality preservation.

The first trimester is a pivotal time for both prenatal and long-term health planning. The more informed you are during this stage, the better prepared you’ll be to advocate for your child’s health - starting at birth and continuing throughout their life.

FAQs

Should I get both NIPT and an NT scan?

Deciding whether to go for both NIPT and an NT scan is a personal decision best made in consultation with your healthcare provider. These are optional first-trimester screenings, each offering unique information.

NIPT is a blood test that screens for chromosomal conditions such as Down syndrome. On the other hand, the NT scan is an ultrasound that can identify physical abnormalities, including heart defects, which NIPT cannot detect.

What does a “no-call” NIPT result mean?

A "no-call" NIPT result means the lab couldn't provide a report, either because there wasn't enough fetal DNA in your blood sample or due to challenges in analyzing it. It's important to note that this result does not mean the fetus has a genetic condition. However, a no-call result can sometimes be associated with a higher chance of aneuploidy. Be sure to discuss this with your healthcare provider - they may recommend retaking the test, seeking genetic counseling, or exploring further diagnostic options.

If my screening is high-risk, what should I do next?

A high-risk result doesn’t guarantee that your baby has a genetic condition. These tests are designed to screen, not diagnose. It’s important to talk with your healthcare provider or a genetic counselor about what this result means and what to do next. They might suggest follow-up diagnostic options, such as CVS (chorionic villus sampling) or amniocentesis, which are known for their high accuracy, or possibly a detailed ultrasound. Deciding whether to proceed with further testing is entirely up to you.