An inconclusive NIPT result means the laboratory was not able to provide a clear result from the sample that was tested. This may also be called a “no result,” “no-call,” “insufficient fetal DNA,” or “low fetal fraction” result, depending on the type of test and the wording used on the report.
For many people, seeing an inconclusive result can feel stressful. It is important to understand that an inconclusive result is not the same thing as a positive result. In many cases, it means there was not enough usable fetal DNA in the mother’s blood sample, the sample did not meet the laboratory’s quality requirements, or the pregnancy-related factors made the test harder to complete.
This can happen with non-invasive prenatal screening tests, prenatal baby gender blood tests, and non-invasive prenatal paternity tests that rely on fetal DNA from the mother’s blood. Below, we explain the most common reasons a prenatal DNA test can come back inconclusive, what low fetal fraction means, and what you may be able to do next.
What Does an Inconclusive NIPT Result Mean?
NIPT stands for non-invasive prenatal testing. It usually refers to a blood test performed during pregnancy to screen for certain chromosome conditions. The test analyzes cell-free DNA in the mother’s blood, which includes DNA from the pregnancy.
An inconclusive NIPT result means the lab could not generate a clear result from the sample. This does not automatically mean that something is wrong with the baby. It means the test could not provide enough reliable information to report a clear answer.
People may describe this result in different ways, including:
- Inconclusive NIPT
- NIPT test inconclusive
- NIPT test came back with no results
- No-call NIPT result
- Insufficient fetal DNA
- Low fetal fraction
- Prenatal DNA test no result
The next step depends on the reason for the inconclusive result, how far along the pregnancy is, and the type of test being performed.
Is an Inconclusive Result the Same as a Positive Result?
No. An inconclusive result is not the same as a positive, high-risk, or abnormal result.
A positive or high-risk result means the test found a signal that may suggest an increased chance of a certain condition. An inconclusive result means the test could not produce a clear answer from the sample.
That distinction matters. If your result is inconclusive, you should not assume the worst. You should speak with your healthcare provider or the testing laboratory to understand why the result happened and whether a redraw, repeat sample, ultrasound, diagnostic testing, or another next step is recommended.
The Most Common Reason: Low Fetal Fraction
One of the most common reasons for an inconclusive NIPT result is low fetal fraction.
Fetal fraction is the percentage of cell-free DNA in the mother’s blood sample that comes from the pregnancy. In simple terms, it tells the laboratory how much fetal DNA is available in the sample compared to maternal DNA.
If the fetal fraction is too low, the laboratory may not have enough fetal DNA to complete the test reliably. This can lead to an inconclusive, no-result, or insufficient fetal DNA report.
What Is Fetal Fraction Percentage?
Fetal fraction percentage refers to the proportion of fetal DNA in the maternal blood sample. For example, if a report shows a fetal fraction of 8%, that means approximately 8% of the cell-free DNA measured in the sample came from the pregnancy.
Different laboratories and different testing methods may have different thresholds for what they consider acceptable. The main point is that the fetal fraction needs to be high enough for the lab to analyze the sample confidently.
Low fetal fraction does not always mean there is a problem with the pregnancy. It can happen because of timing, maternal factors, sample quality, or other pregnancy-related reasons.
Reason 1: Testing Too Early in Pregnancy
Testing too early is one of the simplest reasons a prenatal DNA test may come back inconclusive. Fetal DNA usually increases as pregnancy progresses. If the blood sample is collected too early, there may not be enough fetal DNA in the mother’s bloodstream to complete the analysis.
This can apply to NIPT, prenatal baby gender blood testing, and non-invasive prenatal paternity testing.
At Prenatal Genetics Laboratory, the non-invasive prenatal paternity test can be performed from 8 weeks of pregnancy onward. If there is insufficient fetal cell DNA in the maternal blood sample, a second blood sample collection later in the pregnancy may be recommended.
If your test came back inconclusive and it was taken very early, the lab or your healthcare provider may recommend waiting and collecting a new blood sample later, when the fetal DNA level may be higher.
Reason 2: Low Fetal Fraction
Low fetal fraction is closely related to early testing, but it can also happen even when the sample is collected after the minimum testing window.
Several factors may affect fetal fraction, including:
- Gestational age
- Maternal weight or BMI
- How the sample was collected
- How the blood sample was stored or shipped
- Pregnancy-specific factors
- Laboratory quality thresholds
When the fetal fraction is too low, the lab may not be able to separate or analyze enough fetal DNA to produce a reliable result. In that situation, the safest outcome is often to request a redraw or report the result as inconclusive rather than issue an answer that does not meet quality standards.
Reason 3: Maternal Weight or BMI
Higher maternal weight or BMI can be associated with lower fetal fraction in a blood sample. This is not because the pregnancy is necessarily unhealthy. It can happen because there may be a higher amount of maternal cell-free DNA in circulation, making the fetal DNA proportion lower.
When the fetal fraction is too low, the lab may not be able to complete the test. Depending on the situation, a redraw later in pregnancy may increase the chance of getting a conclusive result.
This is one reason it is important not to panic if a result comes back inconclusive. The issue may be related to sample biology rather than a clear sign of a problem.
Reason 4: IVF, Twins, or Complex Pregnancy Factors
Some pregnancies are more complex for prenatal DNA testing.
For example, IVF pregnancies, twin pregnancies, vanishing twin situations, or other pregnancy-related factors may make interpretation more difficult. Multiple pregnancies can involve more than one fetal DNA contribution, which may make some types of testing more complex or less straightforward.
If you are pregnant with twins, had an early vanishing twin, conceived through IVF, or have been told your pregnancy has unique circumstances, tell the laboratory or healthcare provider before testing. This helps them determine whether the test is appropriate and what limitations may apply.
Reason 5: Sample Collection, Shipping, or Processing Issues
Sometimes an inconclusive result is not caused by fetal fraction alone. A blood sample may also fail to meet testing standards because of collection, handling, shipping, storage, contamination, or processing issues. If you are concerned that a sample may have been handled incorrectly, you can also read our guide on whether a prenatal paternity test can be contaminated.
Possible sample-related issues include:
- Not enough blood collected
- Incorrect blood collection tubes
- Delayed shipment
- Temperature or storage issues
- Damaged sample during transit
- Sample quality below laboratory standards
- Incomplete forms or labelling issues
When a sample does not meet quality standards, the laboratory may request a new sample instead of issuing a result.
Can a Non-Invasive Prenatal Paternity Test Be Inconclusive?
Yes. A non-invasive prenatal paternity test can be inconclusive if there is not enough usable fetal DNA in the maternal blood sample or if the submitted samples do not meet laboratory requirements.
A non-invasive prenatal paternity test uses a blood sample from the pregnant mother and DNA samples from the potential father or fathers. The laboratory analyzes fetal DNA from the maternal blood sample and compares it with the DNA profile of the tested potential father.
If the fetal DNA level is too low, if the blood sample is collected too early, or if there is a sample quality issue, the lab may not be able to complete the analysis. In that case, a second maternal blood sample later in pregnancy may be recommended.
What Happens If a Prenatal Paternity Test Is Inconclusive?
If a prenatal paternity test is inconclusive, the next step depends on why the result could not be completed.
The laboratory may recommend:
- Repeating the maternal blood draw later in pregnancy
- Recollecting a potential father’s DNA sample
- Confirming the pregnancy timing
- Testing all possible fathers if more than one person may be the biological father
- Reviewing whether the pregnancy involves twins, IVF, or other complicating factors
- Checking whether sample collection or shipping instructions were followed properly
At Prenatal Genetics Laboratory, if there is insufficient fetal cell DNA in the mother’s blood sample and the first sample was collected at least 8 weeks into pregnancy, a second blood sample collection later in the pregnancy may be recommended.
What If the NIPT Test Came Back With No Results Twice?
If a NIPT test came back with no results twice, you should speak with your healthcare provider or the laboratory that performed the test. A second inconclusive result can happen, especially when fetal fraction remains low or there are other pregnancy or sample-related factors involved.
A repeated inconclusive result does not automatically mean something is wrong, but it does deserve proper follow-up. Depending on the situation, your provider may discuss options such as another redraw, ultrasound, alternative screening, genetic counselling, or diagnostic testing.
For prenatal paternity testing, the lab may recommend waiting until later in the pregnancy before collecting another maternal blood sample, especially if the earlier samples had insufficient fetal DNA.
Can an Inconclusive Result Happen With a Baby Gender Blood Test?
Yes. A prenatal baby gender blood test may also be affected by fetal DNA levels. If the sample does not contain enough usable fetal DNA, or if the sample is collected too early, the laboratory may not be able to provide a clear result.
This is why timing and sample quality matter. A baby gender blood test, NIPT, and non-invasive prenatal paternity test may have different purposes, but they all rely on fetal DNA being present in the mother’s blood sample at a level that can be analyzed.
How to Reduce the Chance of an Inconclusive Prenatal DNA Test
Not every inconclusive result can be prevented, but there are steps that can reduce the chance of avoidable problems.
Before testing, make sure you:
- Confirm how many weeks pregnant you are
- Follow the laboratory’s timing requirements
- Tell the lab or provider if you are pregnant with twins or conceived through IVF
- Use the correct blood collection tubes and sample materials
- Follow all sample collection instructions carefully
- Ship the sample back as instructed
- Avoid delays in returning the sample
- Test all possible fathers when ordering prenatal paternity testing, when possible
- Contact the lab before collection if you are unsure about anything
Good preparation cannot guarantee a conclusive result, but it can reduce the risk of preventable sample problems.
When Should You Contact the Laboratory?
Contact the laboratory or your healthcare provider if:
- Your result says inconclusive, no result, no-call, low fetal fraction, or insufficient fetal DNA
- You are unsure how far along the pregnancy is
- You tested very early in pregnancy
- You are pregnant with twins or had a possible vanishing twin
- The pregnancy was conceived through IVF
- You need prenatal paternity testing and there is more than one potential father
- You think the blood sample or cheek swab may have been collected incorrectly
- Your NIPT test came back with no results more than once
It is better to ask questions before retesting than to repeat the same issue with another sample.
Frequently Asked Questions About Inconclusive NIPT and Prenatal Paternity Results
What does an inconclusive NIPT result mean?
An inconclusive NIPT result means the laboratory could not provide a clear result from the blood sample. This may happen because of low fetal fraction, insufficient fetal DNA, sample quality issues, early testing, or pregnancy-related factors.
Is an inconclusive NIPT result bad?
Not necessarily. An inconclusive result is not the same as a positive or high-risk result. It means the test could not generate a clear answer. You should speak with your healthcare provider or the testing laboratory about the next step.
Why is my NIPT test inconclusive?
Common reasons include low fetal fraction, testing too early, higher maternal BMI, twins, IVF, sample collection issues, or the blood sample not meeting laboratory quality standards.
What is low fetal fraction?
Low fetal fraction means there was not enough fetal DNA in the mother’s blood sample for the laboratory to complete the test reliably. Fetal fraction can be affected by pregnancy timing, maternal factors, sample quality, and other pregnancy-related issues.
What is fetal fraction percentage?
Fetal fraction percentage is the percentage of cell-free DNA in the mother’s blood sample that comes from the pregnancy. The fetal fraction must be high enough for the laboratory to analyze the sample confidently.
Can a prenatal paternity test be inconclusive?
Yes. A non-invasive prenatal paternity test can be inconclusive if there is not enough usable fetal DNA in the maternal blood sample or if one of the submitted samples does not meet laboratory requirements.
What happens if my prenatal paternity test is inconclusive?
The laboratory may recommend a second maternal blood sample later in pregnancy, recollection of another sample, or review of the pregnancy timing and submitted participant samples.
What if my NIPT test came back with no results twice?
If your NIPT test came back with no results twice, speak with your healthcare provider or the laboratory. They may recommend another redraw, ultrasound, alternative screening, genetic counselling, or diagnostic testing depending on your situation.
Can a baby gender blood test be inconclusive?
Yes. A baby gender blood test may be inconclusive if the sample does not contain enough usable fetal DNA, if the test was performed too early, or if the sample did not meet laboratory requirements.
Can I prevent an inconclusive prenatal DNA test?
You cannot prevent every inconclusive result, but you can reduce the risk by testing at the correct time, following sample collection instructions, using the right collection materials, shipping samples properly, and telling the lab about twins, IVF, or other pregnancy factors before testing.
