Can You Do a NIPT Test at 9 Weeks?

Most labs and professional guidelines set ten weeks of gestation as the earliest point for non-invasive prenatal testing, but a growing body of research shows that NIPT can produce reliable results at nine weeks and sometimes even earlier. The reason for the ten-week standard is practical, not absolute: a key biological threshold tends to be met more consistently after that mark. Whether testing at nine weeks makes sense for you depends on the technology your provider uses, your body weight, and how comfortable you are with a slightly higher chance of needing a second blood draw.

Why Most Labs Draw the Line at Ten Weeks

NIPT works by analyzing tiny fragments of DNA floating in your blood. Despite being called “fetal” DNA, these fragments actually come from the placenta, shed as its outer cell layer constantly renews itself.¹ The placenta and the baby share the same genetic blueprint in the vast majority of pregnancies, so counting chromosome copies in those placental fragments gives a highly accurate picture of the baby’s chromosomes.

The catch is that these placental fragments make up only a small share of all the cell-free DNA circulating in your bloodstream. The rest is yours. The proportion that comes from the placenta is called the fetal fraction, and the lab needs it to be high enough to distinguish a genuine chromosome signal from background noise. Most platforms set a minimum fetal fraction around 4%. Below that threshold, the lab either cannot produce a result or the result is unreliable.

Fetal fraction rises as the placenta grows. Earlier in pregnancy there is simply less placental tissue doing the shedding. Gestational age and body mass index both influence fetal fraction, with higher BMI and earlier gestational age each independently pulling it down.² By ten weeks, the placenta has usually grown enough that the vast majority of samples clear that 4% floor comfortably. That is why ten weeks became the industry standard, not because anything magical happens at that exact day, but because inconclusive-result rates drop sharply once you cross it.

What Research Says About Testing Before Ten Weeks

Several studies have specifically evaluated NIPT before ten weeks and found that it can work well. A 2024 study using a counting-based assay called Vanadis tested pregnancies between six and nine weeks and correctly identified fetal sex in all successful cases, with results matching the standard twelve-week test. No aneuploidies were present in that group, but normal chromosome counts were confirmed in every case.³

A larger clinical feasibility study looked directly at NIPT performed before ten weeks and concluded that once the fetal fraction clears the adequacy threshold, gestational age itself does not independently predict whether a sample will fail. In plain terms, a nine-week sample with adequate fetal fraction performs just as well as a twelve-week sample. The study described early first-trimester NIPT as having “acceptable analytical feasibility and reliable performance.”⁴

So the evidence increasingly suggests that nine weeks is workable. The tradeoff is a somewhat higher probability of getting a “no-call” result, meaning the lab could not produce an answer and you would need a redraw, typically a couple of weeks later. For many people, the chance to get screening information a week sooner is worth that small added risk of a second blood draw.

How Body Weight Changes the Equation

If there is one variable that matters more than gestational age when it comes to early NIPT, it is maternal weight. People with higher BMIs tend to have more of their own cell-free DNA circulating, which dilutes the placental fraction. The placenta is producing the same amount of DNA, but it is a smaller percentage of the total pool.

The numbers are striking. One study found that women with a normal BMI had an average fetal fraction of about 12.5%, while women classified as obese averaged about 9.2%. The rate of inconclusive results jumped from roughly 1.7% in the normal-weight group to 8.4% in the obese group.⁵ Another large study confirmed that low fetal fraction occurred in about 4.5% of normal-weight women but in roughly 20% of obese women and over a third of those with severe obesity.⁶

This effect compounds with early gestational age. A study examining weight categories week by week found that at nine to twelve weeks, the no-call rate in people under 150 pounds was only 0.14%, while in those over 400 pounds it reached about 17%.⁷ Fetal fraction does increase with each passing week, but the weekly gain is smaller at higher body weights. In the heaviest weight category, fetal fraction rose only about half a percentage point per week.⁷

The practical takeaway: if you are at a lower body weight, testing at nine weeks carries very little extra risk of an inconclusive result compared to ten weeks. If your BMI is significantly elevated, waiting even an extra week or two can meaningfully improve the odds of getting a clear answer on the first draw.

Newer Technologies That Push the Window Earlier

Standard NIPT platforms read all the cell-free DNA in a blood sample and use bioinformatics to figure out how much of it is placental. Some newer approaches try to enrich the placental fraction before sequencing, essentially filtering out more of the maternal DNA so the fetal signal is amplified.

A recent study using in vitro fetal enrichment tested samples drawn between eight and nearly ten weeks. Without enrichment, about 31% of those early samples had a fetal fraction below 4%, which would normally mean a failed test. With enrichment, that figure dropped to roughly 4%, meaning about 95% of samples drawn after eight weeks yielded a usable fetal fraction.⁸ That is a dramatic improvement and suggests that the ten-week cutoff may become a relic as lab methods improve.

The technology you have access to matters as well. Some labs use whole-genome sequencing approaches that will report a result even at very low fetal fractions, while single-nucleotide polymorphism methods have a built-in fetal-fraction cutoff and will flag the sample as failed if it falls below that line.⁹ A lab that reports results at low fetal fractions is not necessarily doing you a favor, because accuracy at very low fractions is less certain. The SNP-based approach of declining to report below a threshold is more conservative, but it protects you from an unreliable result.

One caveat the enrichment study flagged: spontaneous miscarriage rates before twelve weeks are higher than most people realize. Getting a NIPT result at eight or nine weeks and then losing the pregnancy shortly afterward is emotionally complicated, and it is something to consider when weighing how early to test.

What Happens When a Result Comes Back Inconclusive

An inconclusive or “no-call” result does not mean something is wrong with the baby. In most cases it means the fetal fraction was too low for the lab to make a reliable call. The usual next step is a redraw two to three weeks later, giving the placenta more time to grow and shed DNA.

How likely is a redraw to succeed? One study found that about 84% of redrawn samples produced a reportable result, with no increased rate of aneuploidy in that group compared to the general screening population.¹⁰ Another study reported an overall redraw success rate of about 63%, with the success heavily dependent on three factors: the fetal fraction on the initial draw, the time between blood draws, and maternal weight. If the initial fetal fraction was above 3%, the success rate was over 70%; below 2%, it dropped to under 30%.¹¹ Waiting at least two to three weeks before the redraw also helped, with success rates climbing about 15% per week over the first three weeks.¹¹

Some labs combine the fetal fraction data from a failed result with a risk algorithm that can flag certain aneuploidies even without a full screen. One analysis found that among women with an initially uninformative NIPT who had a redraw, about 80% ultimately received usable risk information, either from the algorithm itself or from a successful second draw.¹²

If you choose to test at nine weeks and get an inconclusive result, the redraw will likely land around eleven or twelve weeks, which is still well within the first trimester. That timing actually aligns with when most providers would have ordered the test under the standard guideline anyway, so you have not really lost anything by trying early.

Medications That Can Interfere

One factor that rarely gets mentioned in patient-facing materials is anticoagulant medication. Blood thinners like low-molecular-weight heparin are commonly prescribed during pregnancy, and they appear to lower fetal fraction substantially. A study found that women on anticoagulation had a fetal fraction of about 9.3% compared to 11.7% in those not taking blood thinners. More strikingly, the inconclusive-result rate was 17.2% in the anticoagulation group, compared to just 2.7% otherwise.¹³

The mechanism seems to involve a spike in total cell-free DNA concentration. Anticoagulants may reduce the clearance of all circulating DNA fragments or promote their release, flooding the sample with maternal DNA and making the fetal signal harder to detect. If you are on blood thinners and considering early NIPT, this is worth discussing with your provider. Waiting a week or two longer or choosing a platform with enrichment technology could improve your chances of a clear result on the first draw.

Vanishing Twins and False Positives

NIPT screens the placenta, not the baby directly. That distinction usually does not matter because the placenta and fetus are genetically identical. But in some situations, the DNA the lab is reading does not reflect the baby you are carrying. One well-documented example is the vanishing twin: an early twin pregnancy in which one embryo stops developing and is gradually reabsorbed, while the surviving twin continues normally.

The problem is that the placental tissue from the demised twin can keep shedding DNA into your bloodstream for weeks after it stops developing. One case report documented a vanishing trisomy-14 twin contributing to the cell-free DNA pool for more than two weeks after demise, producing a discordant NIPT result for the surviving healthy twin.¹⁴

A large Dutch study found that in vanishing-twin pregnancies where the demise happened later (with a visible embryonic pole), the rate of abnormal NIPT results was 12.6%, compared to 1.7% in earlier vanishing twins. Among those flagged positive for trisomy 21, only about 41% were confirmed in the surviving baby. None of the positive results for trisomy 18, trisomy 13, or other chromosomal findings were confirmed in the living fetus.¹⁵ A systematic review of the broader literature found similar patterns: NIPT detected true trisomy 21 cases in vanishing-twin pregnancies, but the false-positive rate was considerably elevated.¹⁶

This is relevant to the nine-week question because vanishing twins are more likely to be detected at very early ultrasounds. If you had bleeding or an early scan showed a second gestational sac that later disappeared, your provider should factor that into how they interpret any NIPT result, regardless of when the blood was drawn.

Other sources of false positives include confined placental mosaicism, where the placenta carries a chromosomal abnormality that the baby does not, and maternal copy-number variations, small duplications in the mother’s own DNA that can mimic a fetal trisomy signal. One study found that in about 8% of false-positive trisomy cases, the mother carried a non-pathogenic duplication on the relevant chromosome that was inflating the lab’s measurement.¹⁷ These biological confounders are reasons why NIPT is classified as a screening test, not a diagnostic one.

Why a Positive NIPT Always Needs Confirmation

Regardless of whether you test at nine weeks, ten weeks, or later, a positive NIPT result should be confirmed with a diagnostic procedure. The two options are chorionic villus sampling, which can be done starting around eleven weeks, and amniocentesis, which is typically performed after about fifteen and a half weeks.

CVS is faster and can be performed earlier, which matters if early decision-making is important to you. But because CVS samples the placenta, and the placenta is exactly where some of the confounders described above originate, some researchers argue that amniocentesis is the better confirmatory choice when ultrasound findings look normal. Amniocentesis samples the amniotic fluid, which contains cells shed by the baby itself, so it sidesteps placental mosaicism entirely.¹⁸

The tension between these two approaches is real. If NIPT flags something at nine or ten weeks, you could potentially have CVS at eleven or twelve weeks and get an answer fairly quickly. But if the NIPT result turns out to be a false positive due to confined placental mosaicism, the CVS might see the same mosaicism and not resolve anything. Amniocentesis provides a cleaner answer but means waiting until at least fifteen and a half weeks.¹⁹ Your provider and genetic counselor can help you weigh the timing against the type of abnormality flagged, since some findings are more likely to reflect true fetal problems than others.

What the Official Guidelines Say

The American College of Medical Genetics and Genomics recommends NIPT from ten weeks of gestation onward for the general-risk population.²⁰ Most professional societies around the world align with this threshold. Insurance coverage also typically follows the guidelines, so a test drawn at nine weeks might not be covered under the same codes, depending on your carrier.

Guidelines tend to lag behind research, and the studies supporting NIPT before ten weeks have accumulated mostly in the last few years. It is entirely possible that official recommendations will shift earlier as enrichment technologies mature and larger validation studies are published. For now, the practical situation is that some providers will order NIPT at nine weeks, particularly if you have a clinical reason for wanting early results, while others will ask you to wait until ten weeks because that is what the guidelines recommend and what the lab’s validation data covers.

If your provider is willing to order the test at nine weeks and you understand that the chance of needing a redraw is modestly higher, there is no safety concern. The test is just a blood draw from your arm. The only cost of testing early and getting an inconclusive result is a second blood draw and a few more weeks of waiting, which puts you right back where you would have been under the standard timeline.

When Cell-Free DNA First Becomes Detectable

Placental DNA fragments are actually present in the mother’s bloodstream far earlier than most people assume. Research has detected cell-free fetal DNA in maternal plasma from about five weeks of gestation.²¹ The reason we cannot screen at five weeks is not that the DNA is absent but that its concentration is far too low relative to the mother’s DNA for current platforms to produce reliable chromosome calls. The research into fetal enrichment techniques is essentially an arms race against that dilution problem, trying to isolate more of the placental signal from a smaller starting pool. The Vanadis system that demonstrated success at six to nine weeks uses a different counting method that may be less sensitive to low fetal fraction than sequencing-based approaches, which is part of why it performed well at such early gestational ages.³ As more platforms are validated for early use, the window for NIPT will likely continue to inch earlier, with nine weeks eventually becoming routine and eight weeks following closely behind.