“The NT scan looks reassuring. Do we still need the blood test?” This is a common question during early pregnancy, especially when an older child is healthy or there is no known family history of a genetic condition.
If you are considering the Double Marker Test After NT Scan, the key question is which screening plan your doctor has recommended. In combined first-trimester screening, the ultrasound and blood test contribute different pieces of information. Completing only the scan may leave that planned assessment incomplete.
Why is a Double Marker Test After NT Scan advised?
An NT scan measures the fluid-filled space behind the baby’s neck. The Double Marker blood test measures two substances: pregnancy-associated plasma protein-A (PAPP-A) and free beta-hCG. These measurements, together with maternal age and pregnancy dating information, can be used to calculate a combined chance estimate for certain chromosomal conditions.
Depending on the laboratory’s screening protocol, the report may assess Down syndrome (trisomy 21), Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13). Ask your doctor which conditions your particular test covers.
NT scan and blood test: two parts of combined screening
Different information, one assessment
Think of the scan and blood sample as complementary parts of the screening plan. Neither should be treated as a guarantee about every aspect of the baby’s health.
Does a normal NT scan mean the blood test is unnecessary?
A reassuring NT measurement is encouraging, but it cannot exclude all chromosomal conditions. It also does not provide the blood-marker information needed for a combined screening calculation.
For example, a family may hear that the scan looks normal and assume the entire screening process is finished. If combined screening was prescribed, the next useful step is to ask: “Is our combined result complete, or do we still need to give the blood sample?” This is clearer than making a decision from the scan report alone.
What if your previous pregnancy was healthy?
It is understandable to feel reassured by an earlier uncomplicated pregnancy. However, each pregnancy needs its own assessment. Some chromosomal changes occur without a known family history, and a previous child’s health cannot predict the result of screening in the current pregnancy.
Share your complete history with your obstetrician, including previous pregnancies and any genetic test results. That history helps guide counselling, but it is not a substitute for discussing the current options.
Ask about this pregnancy’s screening plan
If cost, timing or uncertainty is making you hesitate, say so. Ask what information the test adds and how the result could influence your next steps.
Doctor counselling a pregnant couple
When should the scan and blood test be done?
First-trimester screening is time-sensitive. The NT scan is commonly scheduled around 11 weeks to 13 weeks 6 days, subject to the baby’s size and the centre’s protocol. The blood sample also has a laboratory-specific accepted window. Confirm your exact dates instead of waiting until the last day.
If the scan is already done, contact your doctor or laboratory promptly to check whether you are still within the blood-test window and which scan details they need. If you have missed the window, ask about suitable alternatives for your stage of pregnancy.
For appointment planning, read our NT and anomaly scan preparation guide. If you are uncertain about your pregnancy dates, our guide to how pregnancy weeks are calculated explains why the dates can feel confusing.
How should you understand the result?
A screening report may describe a lower or higher chance and show a ratio. For example, a chance of 1 in 100 is higher than 1 in 1,000. These numbers describe probability, not certainty. The threshold used to classify a result depends on the screening programme or laboratory.
A lower-chance result is reassuring for the conditions assessed, but it cannot rule out every condition. A higher-chance result also does not mean the baby definitely has a chromosomal condition. Your doctor will explain the report and the available follow-up.
Follow-up may involve counselling, further ultrasound assessment, NIPT or diagnostic testing such as chorionic villus sampling or amniocentesis. NIPT remains a screening test. Diagnostic procedures can provide confirmation for the conditions tested, and their benefits, limitations and risks should be discussed individually.
Reviewing the combined screening report
Review the full report with your doctor
Avoid judging the result from one number, an online comparison or another family’s experience. Bring both the scan and blood reports to the consultation.
Is the Double Marker test needed in every screening plan?
Not necessarily. Combined screening is one approach; NIPT is another screening option that may be discussed. The appropriate choice depends on your preferences, clinical circumstances, availability and cost. If you have already had NIPT, tell your doctor before arranging another screening test.
Adding several independent screening tests without a coordinated plan can complicate interpretation. Ask which approach you are following and what each additional test is intended to answer. Screening is voluntary, and an informed discussion should support your decision.
Before you decide: five questions to ask
- Are we following combined first-trimester screening or another approach?
- What does the blood test add to my NT scan result?
- What is the last suitable date for my blood sample?
- Which conditions will the report assess, and what can it miss?
- What would the next step be after a lower- or higher-chance result?
Bring your prescription, NT report and previous pregnancy records. For help preparing for an earlier ultrasound, see early pregnancy scan mistakes to avoid.
Watch: NT scan done—can you skip the Double Marker test?
Watch the Nisarga Diagnostics reel, then discuss any questions with your treating doctor.
Frequently asked questions
Is the Double Marker blood test the same as an NT scan?
No. The NT scan is an ultrasound measurement. The blood test measures biochemical markers in the mother’s blood. They provide different information and may be combined in one screening assessment.
My NT scan is normal. Should I still do the blood test?
If your doctor has selected combined first-trimester screening, ask whether the blood test is still needed to complete it. A reassuring ultrasound measurement alone is not the completed combined result.
My first baby was healthy. Can I skip screening in this pregnancy?
A previous healthy baby does not rule out chromosomal conditions in a later pregnancy. Discuss screening for the current pregnancy rather than relying only on previous outcomes.
Is screening compulsory?
Screening is a choice. Your doctor should explain the purpose, limitations, alternatives and possible next steps so you can make an informed decision.
Does a higher-chance result mean my baby definitely has a condition?
No. It means further discussion and assessment are appropriate. Screening alone cannot confirm a chromosomal diagnosis.
What if my blood result and NT report seem different?
Do not interpret them as separate pass-or-fail tests. Ask whether a combined report has been issued and have your doctor review the complete information.
Do the scan and blood sample need to happen on the same day?
Not necessarily. The laboratory must receive the required scan details and the sample within its accepted testing window. Confirm the schedule with your doctor and laboratory.
Do I need to fast for the Double Marker test?
Fasting is generally not required for this blood test alone. Check the laboratory’s instructions, especially if other blood tests have been ordered at the same visit.
What if I have already had NIPT?
Tell your doctor and bring the report. The need for additional serum screening depends on the screening plan; do not add tests independently. Ultrasound assessments may still be needed.
Can these tests replace the anomaly scan?
No. Chromosomal screening and a detailed assessment of the baby’s anatomy have different purposes. Attend the later anomaly scan at the time advised by your obstetrician.
Planning pregnancy screening in Sanjaynagar, Bengaluru
At Nisarga Diagnostics, Sanjaynagar, Bengaluru, ask the team about your prescribed scan’s appointment timing and the records to bring. Confirm blood-test arrangements and the complete screening pathway with your obstetrician and the relevant laboratory.
The most useful next step after an NT scan is to understand whether your recommended screening is complete. Review the options and results with your doctor before deciding which tests to pursue.
Founder of Nisarga Diagnostics, is a renowned fetal ultrasound specialist with over 20 years of expertise. An alumnus of Government Medical Colleges in Mysore and Bangalore, he also holds a D.N.B. from the National Board of Examinations, Delhi, and certification from the Fetal Medicine Foundation, London. A former Professor and HOD, he has trained countless PG students and junior radiologists, shaping the future of fetal imaging in India.