Sequenom Laboratories occupies a pivotal place in the story of prenatal diagnostics: it brought the first commercially available cell-free DNA screening test to market in the United States, launching MaterniT21 in October 2011 and setting off a transformation in how pregnancies are screened for chromosomal abnormalities. The company’s path from a mass-spectrometry genotyping firm to a household name in prenatal care was anything but smooth, involving scientific breakthroughs it did not originate, a data falsification scandal that nearly derailed its ambitions, and an eventual acquisition that folded its technology into one of the largest laboratory networks in the world. Understanding Sequenom’s trajectory means understanding the broader arc of noninvasive prenatal testing itself.
The Science That Made Everything Possible
The foundation for Sequenom’s prenatal testing business was laid in 1997, when researcher Dennis Lo and colleagues demonstrated that fragments of fetal DNA circulate freely in a pregnant person’s blood plasma. Working with plasma samples from women carrying male fetuses, Lo’s team detected fetal Y-chromosome sequences in about 80% of maternal plasma samples, using as little as ten microliters of material. None of the women carrying female fetuses or the non-pregnant controls tested positive, confirming that the DNA was genuinely fetal in origin.1The Lancet. Presence of cell-free fetal DNA in maternal plasma and serum The paper’s closing line noted that this finding “may have implications for non-invasive prenatal diagnosis,” which proved to be one of the more consequential understatements in modern obstetrics.
Follow-up work quickly established that cell-free fetal DNA was a far better target than the approach researchers had been pursuing for years: trying to isolate intact fetal cells from the mother’s bloodstream. Comparisons showed that the cell-free method was at least four times more sensitive for detecting chromosomal abnormalities than intact-cell approaches.2PubMed. Cell-free fetal DNA and intact fetal cells in maternal blood circulation: implications for first and second trimester non-invasive prenatal diagnosis By the early 2000s, researchers recognized that maternal plasma containing both fetal and maternal DNA opened up genuinely new possibilities for noninvasive prenatal diagnosis.3Clinical Chemistry. Fetal DNA in Maternal Plasma: Biology and Diagnostic Applications The question was no longer whether it could be done, but who would figure out how to do it reliably at scale.
Sequenom’s Origins in Mass Spectrometry
Sequenom did not start out in prenatal testing. The company was founded in 1994 in San Diego, and its core technology was a platform called MassARRAY, which used a type of mass spectrometry to identify genetic variations. The system worked by amplifying a region of DNA around a point of interest, extending a small probe by a single base at the variant site, and then measuring the precise mass of that extended probe. Different genetic variants produced molecules of slightly different masses, and the instrument could distinguish them with high accuracy.4Current Protocols in Human Genetics. SNP Genotyping Using the Sequenom MassARRAY iPLEX Platform
This approach carved out a niche in the genomics world. Mass spectrometry had been identified early on as a promising tool for analyzing sequence variation, and by the mid-2000s, primer-extension methods combined with this detection technology had become the standard for large-scale genotyping studies in the field.5PubMed. DNA analysis by MALDI-TOF mass spectrometry Sequenom’s MassARRAY platform found applications well beyond human genetics: researchers adapted it for tasks as varied as typing drug-resistant bacteria, using multiplexed assays that could interrogate many genetic markers simultaneously.6PubMed. Comparison of a multiplexed MassARRAY system with real-time allele-specific PCR technology for genotyping of methicillin-resistant Staphylococcus aureus The company had a respected genotyping platform, but it was looking for a larger commercial opportunity. Prenatal testing seemed like one.
The Scandal and the Pivot
In the late 2000s, Sequenom was developing a noninvasive prenatal test for Down syndrome based on cell-free fetal DNA. Expectations were high, and the company’s stock price reflected investor enthusiasm. Then, in 2009, Sequenom disclosed that data supporting its prenatal test had been manipulated by a researcher on its development team. The revelation was devastating. Clinical trials were halted, the company’s stock collapsed, executives departed, and lawsuits followed. For a time, it looked as though Sequenom might never enter the prenatal testing market at all.
The company regrouped. Rather than continuing to develop its original mass-spectrometry-based approach to fetal DNA analysis, Sequenom shifted to a different technical strategy: massively parallel sequencing, sometimes called next-generation sequencing. This method works by sequencing millions of short DNA fragments from maternal plasma simultaneously and then counting how many fragments map to each chromosome. If a fetus has an extra copy of chromosome 21, for instance, a slightly higher proportion of sequenced fragments will come from that chromosome than expected. The approach was robust, scalable, and ultimately vindicated Sequenom’s bet on the prenatal market.
MaterniT21 and the Birth of Commercial NIPT
In October 2011, Sequenom became the first company to launch a sequencing-based noninvasive prenatal test in the United States. The product, called MaterniT21, initially screened for trisomy 21 (Down syndrome) and was soon expanded to cover trisomy 18 (Edwards syndrome), trisomy 13 (Patau syndrome), and sex chromosome abnormalities.7PubMed Central. Commercial Landscape of noninvasive prenatal testing in the United States – Section: Commercial Landscape of cffDNA-based NIPT The test was initially marketed to women considered high-risk for chromosomal abnormalities, typically those over 35 or with abnormal results from traditional screening.
Competitors followed quickly. Within a year or so of MaterniT21’s launch, several other companies entered the NIPT market with their own cell-free DNA tests, including Verinata Health (later acquired by Illumina), Ariosa Diagnostics, and Natera. But Sequenom’s first-mover status gave it early brand recognition and a significant share of the market. The test’s expanded version, MaterniT21 PLUS, eventually added detection for select microdeletions and other chromosomal abnormalities, broadening the range of conditions a single blood draw could screen for.
Clinical validation studies confirmed strong performance. In a large study published in the New England Journal of Medicine, cell-free DNA testing detected trisomy 21 with 100% sensitivity, with a false positive rate of just 0.06% and a positive predictive value of about 81%.8PubMed. Cell-free DNA Analysis for Noninvasive Examination of Trisomy Across different commercial implementations, sensitivity and specificity for the major trisomies exceeded 99%, with fetal sex classification accuracy around 99.3% as well.9PubMed Central. Application of risk score analysis to low-coverage whole genome sequencing data for the noninvasive detection of trisomy 21, trisomy 18, and trisomy 13 These numbers represented a dramatic improvement over older screening methods like the first-trimester combined screen, which had substantially higher false positive rates.
How Risk Level Affects What the Results Mean
One of the most misunderstood aspects of NIPT is the difference between sensitivity and positive predictive value. A test can detect nearly all true cases of a condition (high sensitivity) while still producing a meaningful number of false alarms in populations where the condition is rare. This distinction matters because it shapes what a positive result actually means for the individual patient.
For trisomy 21, the positive predictive value depends heavily on the population being tested. In clinical laboratory data, observed positive predictive values for trisomy 21 ranged from about 97% in women under 30 to over 99% in women aged 35 to 39, though the value dipped slightly in women over 40.10PubMed. Observed and Modeled Positive Predictive Values Using Cell-free DNA Testing for Fetal Trisomy in a Clinical Laboratory Population For rarer conditions like trisomy 18 and trisomy 13, the predictive values were lower, ranging from roughly 77% to 97% for trisomy 18 and from about 30% to 80% for trisomy 13, depending on patient age and risk group.
When researchers compared results across risk categories directly, the gap was even clearer. In one study, the positive predictive value for all three trisomies combined was about 74% in a lower-risk group compared to about 94% in a higher-risk group.11American Journal of Obstetrics and Gynecology. Performance of cell-free DNA screening for aneuploidy in low-risk pregnancies – Section: Results The practical takeaway: NIPT is a screening test, not a diagnostic one. A positive result, especially for the rarer trisomies in a younger or lower-risk patient, still needs confirmation through amniocentesis or chorionic villus sampling. This is a point that clinicians and genetic counselors emphasize repeatedly, and one that patients sometimes miss in the relief of having a “simple blood test.”
Why the Test Sometimes Fails or Misleads
Cell-free DNA screening reads a mixture of maternal and fetal DNA fragments. The proportion that comes from the fetus, known as the fetal fraction, is a critical quality control parameter.12PubMed Central. Factors Affecting the Fetal Fraction in Noninvasive Prenatal Screening: A Review If the fetal fraction is too low, the test cannot reliably distinguish a normal result from an abnormal one, and the laboratory will report a “no call” or non-informative result, requiring a repeat blood draw or an alternative screening method.
The most common reason for a low fetal fraction is higher maternal body mass index. In one population-level analysis, fetal fraction showed a clear negative association with BMI, meaning that as maternal weight increased, the proportion of fetal DNA in the blood decreased.13PLOS ONE. Insights into non-informative results from non-invasive prenatal screening through gestational age, maternal BMI, and age analyses – Section: Results Gestational age works in the opposite direction: later in pregnancy, fetal fraction tends to rise. Maternal white blood cell count is another factor. Research has found that higher white blood cell counts independently reduce fetal fraction, and when combined with elevated BMI, test failure rates can climb substantially, reaching over 7% in some subgroups compared to less than 1% in the lowest-risk groups.14Frontiers in Medicine. White blood cell count affects fetal fraction and test failure rates in noninvasive prenatal screening – Section: Results
Beyond fetal fraction, there are biological situations that can produce genuinely misleading results. Confined placental mosaicism, a condition where the placenta carries a chromosomal abnormality that the fetus does not share (or vice versa), is a well-recognized source of both false positives and false negatives. Because the cell-free fetal DNA in maternal blood comes primarily from the placenta, not the fetus itself, the test is really reading the placenta’s genetics. In one case report, confined placental mosaicism led to a result that was falsely positive for trisomy 21 and simultaneously falsely negative for a sex chromosome abnormality that the fetus actually had.15PubMed Central. Discrepancy between non-invasive prenatal testing result and fetal karyotype caused by rare confined placental mosaicism: A case report – Section: Discussion Estimates suggest the false positive rate from placental mosaicism for the common trisomies ranges from roughly 1 in 1,000 to 1 in 4,000, depending on the degree of mosaicism.16Genetics in Medicine. Fetoplacental mosaicism: potential implications for false-positive and false-negative noninvasive prenatal screening results
The Impact on Invasive Procedures
Before NIPT, the standard pathway for pregnancies flagged as high-risk for chromosomal abnormalities typically led to amniocentesis or chorionic villus sampling. Both procedures involve inserting a needle into the uterus and carry a small but real risk of miscarriage. The availability of a highly accurate blood-based screen changed the calculus for many patients and providers. Adoption of NIPT has been associated with a significant reduction in these invasive diagnostic procedures, improving both physical safety and the psychological experience of prenatal care.17PubMed Central. Non-Invasive Prenatal Testing (NIPT): A Paradigm Shift in Prenatal Care
The scale of the shift has been documented directly. In one study tracking changes over a twelve-year period among women of advanced maternal age, amniocentesis rates dropped from 56% before updated professional guidelines to 38% after a key guideline change, and then plummeted to just 10% after NIPT became available.18PubMed Central. Change in rates of prenatal tests for chromosomal abnormality over a 12-year period in women of advanced maternal age – Section: RESULTS That trajectory, from more than half of eligible patients undergoing an invasive procedure to roughly one in ten, illustrates how quickly NIPT reshaped clinical practice.
Professional Guidelines and the Expansion to All Pregnancies
Initially, professional organizations recommended NIPT only for pregnancies already considered high-risk based on maternal age, ultrasound findings, or prior screening results. That restriction gradually softened. The American College of Medical Genetics and Genomics now strongly recommends cell-free DNA screening over traditional screening methods for all pregnant patients with singleton and twin pregnancies, for trisomies 21, 18, and 13, and also recommends offering it for sex chromosome abnormalities.19Genetics in Medicine. Noninvasive prenatal screening (NIPS) for fetal chromosome abnormalities in a general-risk population: An evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG) – Section: Conclusion Canadian guidelines have followed a similar path, identifying cell-free DNA as the most accurate early prenatal screening method for common trisomies and recommending it be discussed with all pregnant patients.20Journal of Obstetrics and Gynaecology Canada. Guideline No. 456: Prenatal Screening for Fetal Chromosomal Anomalies – Section: SUMMARY STATEMENTS
The shift from high-risk-only to universal offering has expanded the potential market enormously, but it has also introduced new complexities. As noted earlier, positive predictive values are lower in lower-risk populations, which means more patients who screen positive will receive false alarms. Genetic counseling becomes even more important in a universal screening environment, where many patients may not fully understand that a “positive” screen is not a diagnosis.
Acquisition and Afterlife
In 2016, LabCorp, one of the two dominant clinical laboratory companies in the United States, announced its acquisition of Sequenom for roughly $371 million. The deal closed in 2017. MaterniT21 PLUS continued as a product within LabCorp’s women’s health and genetics division, though the Sequenom brand gradually faded from public view. For most patients today, the test is simply one of several NIPT options their obstetrician might offer, alongside Harmony (from Roche, which acquired Ariosa), Panorama (from Natera), and VeriSeq (from Illumina).
The acquisition reflected an industry-wide pattern. The early NIPT market was driven by small, specialized companies racing to commercialize cell-free DNA analysis. Within a few years, nearly all of them were absorbed by larger players. The technology itself proved more durable than any individual corporate identity. Sequenom’s legacy lives on not in its brand name, but in the fact that millions of pregnancies worldwide are now screened with a blood test that did not exist before the company took a chance on commercializing Dennis Lo’s 1997 discovery.
When NIPT Accidentally Detects Cancer
One of the more unexpected developments in the NIPT story has been the incidental detection of maternal cancer. Because the test sequences all cell-free DNA in the mother’s blood, not just the fragments originating from the placenta, tumors that shed abnormal DNA into the bloodstream can produce unusual patterns that do not match typical fetal abnormalities. When a test returns results that seem inconsistent, showing abnormalities scattered across multiple chromosomes rather than a clean signal on chromosome 13, 18, or 21, the cause sometimes turns out to be a previously undiagnosed malignancy in the mother.
In a large early study of over 125,000 NIPT tests, about 3% returned positive for one or more aneuploidies. Among the cases with discordant or unusual results, clinicians voluntarily reported ten cases in which the mother was subsequently diagnosed with cancer, including lymphomas, sarcomas, and various carcinomas.21JAMA. Noninvasive Prenatal Testing and Incidental Detection of Occult Maternal Malignancies – Section: Results More recent and systematic work has sharpened the picture. In a study that followed up on patients with atypical NIPT results showing copy-number changes across three or more chromosomes, cancer was present in nearly 96% of participants with that particular sequencing pattern.22PubMed Central. Prenatal cfDNA Sequencing and Incidental Detection of Maternal Cancer – Section: RESULTS
This was never part of the test’s design, and it raises its own set of clinical and ethical questions. A person undergoing a routine prenatal screen does not necessarily expect to learn that they might have cancer. Laboratories and clinicians are still working out the best protocols for handling these incidental findings, including how to communicate them and what follow-up to recommend. But the phenomenon underscores something broader about cell-free DNA: once you start sequencing everything floating in someone’s blood, you may learn things no one was looking for.
Ethical Tensions and the Cost Question
As NIPT has expanded from high-risk to general-risk populations, the ethical questions have grown more complex. Concerns include the routinization of testing, the possibility that informed consent becomes perfunctory when a blood draw is framed as “just another prenatal screen,” and the implications for disability communities when screening for conditions like Down syndrome becomes widespread and nearly automatic. Researchers have flagged that ensuring accurate, balanced information is available to all patients, and that access to NIPT is equitable across income levels and healthcare systems, requires active policy guidance from regulators, professional societies, and insurers.23PubMed. Noninvasive Prenatal Genetic Testing: Current and Emerging Ethical, Legal, and Social Issues
Cost is part of that equity picture. In countries with nationalized health systems, the decision to offer NIPT to all pregnancies rather than only high-risk ones involves difficult trade-offs. A Spanish cost-effectiveness analysis found that using NIPT as a first-line screening tool for all pregnancies would be more effective at detecting Down syndrome but at a very high incremental cost per additional case detected, running into the range of well over a million euros compared to contingent strategies that reserve NIPT for patients who screen positive on a cheaper initial test.24PubMed Central. The consequences of implementing non-invasive prenatal testing with cell-free foetal DNA for the detection of Down syndrome in the Spanish National Health Service: a cost-effectiveness analysis – Section: Results Many health systems have settled on a compromise: traditional first-tier screening for all, with NIPT offered as a second-tier test for those with elevated risk. The patchwork of coverage and reimbursement policies across countries and even across insurers within a single country means that access to NIPT still depends partly on where you live and what you can pay.
The Expanding Scope of Cell-Free DNA
Sequenom’s original test looked at a handful of chromosomes. Today’s NIPT platforms increasingly offer genome-wide screening, searching for deletions or duplications across all chromosomes, as well as microdeletion syndromes involving small missing segments of DNA. The clinical utility of this broader screening remains debated. For the common trisomies, evidence is strong and performance is well characterized. For rarer conditions, the base rates are so low that even a highly specific test will produce a substantial proportion of false positive results, and the clinical evidence on outcomes is thinner.
Beyond prenatal screening, cell-free DNA analysis has become a growing field in oncology (liquid biopsies for cancer detection and monitoring), transplant medicine (monitoring organ rejection by detecting donor DNA in the recipient’s blood), and even infectious disease. The technology Sequenom helped popularize in the prenatal space has turned out to be a platform with much broader medical applications. The company itself may have been absorbed into a larger corporate structure, but the idea at its core, that fragments of DNA circulating in blood carry actionable medical information, continues to reshape clinical practice across multiple specialties.