How is Non-invasive Chromosomal Screening in China? | Current Status and Clinical Value of NIPT

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Current Development Status of Non-invasive Chromosomal Screening in China

The clinical application of non-invasive chromosomal screening technology in China, with clear indications, is Non-invasive Prenatal Testing (NIPT). Some assisted reproductive centers also use it as a supplementary assessment for preimplantation screening. Since receiving approval from the National Medical Products Administration in 2012, it has been integrated into the prenatal screening systems of most tertiary hospitals and reproductive centers nationwide, with an annual testing volume exceeding 8 million, making it a first-line tool for prenatal chromosomal abnormality screening.

Compared with traditional serological screening (maternal serum screening), NIPT increases the detection rate for trisomy 21 from 60%–70% to over 99%, and reduces the false positive rate from 5% to 0.1%–0.3%. Chinese clinical data show that under standard operating procedures, the positive predictive value (PPV) of NIPT varies significantly depending on the target chromosome: approximately 80%–95% for trisomy 21, 40%–70% for trisomy 18, 20%–40% for trisomy 13, and 15%–40% for sex chromosome abnormalities. This variation stems from the background incidence of the target condition, sequencing depth, and bioinformatics algorithm characteristics, not technical flaws.

Technical Principles and Detection Scope

NIPT is based on high-throughput sequencing platforms, sequencing cell-free fetal DNA (cffDNA) derived from the fetus in maternal peripheral blood. It determines the presence of aneuploidy by comparing the relative amounts of each chromosome. The fetal fraction is a core parameter determining test reliability, typically required to be ≥4%; below this threshold, a report cannot be issued, or a repeat blood draw is necessary.

Current mainstream detection scope includes:

• Autosomal Aneuploidies: Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), Trisomy 13 (Patau syndrome)
• Sex Chromosome Aneuploidies: 45,X (Turner syndrome), 47,XXY (Klinefelter syndrome), 47,XXX, 47,XYY
• Select Microdeletion/Microduplication Syndromes: 22q11.2 deletion (DiGeorge syndrome), 1p36 deletion, 15q11.2 deletion, etc. (depending on the test product)

Data sourced from multi-center clinical validation studies conducted in China from 2020 to 2024. Specific values may vary depending on the testing platform and population composition.

Doctor's Perspective: Clinical Positioning and Limitations of NIPT

Within the prenatal diagnosis system, NIPT is a screening technology, not the diagnostic gold standard. Clinicians position it as a "high-precision screening" tool to replace traditional serological screening and reduce the rate of unnecessary invasive procedures. However, the following points must be clearly understood:

• A "low-risk" NIPT result does not guarantee a completely normal fetal chromosome set—false negatives are possible (especially for trisomy 13 and sex chromosome abnormalities);
• A "high-risk" NIPT result must be confirmed by karyotype analysis via amniocentesis or chorionic villus sampling; pregnancy decisions should not be made solely based on this result;
• NIPT cannot detect chromosomal structural abnormalities (e.g., balanced translocations, inversions), uniparental disomy, or small deletions/duplications;
• NIPT accuracy is lower for twin and multiple pregnancies compared to singletons, particularly when one twin is abnormal, as its discriminatory ability is limited.

Differences in Technology Application Across Countries

Compared with developed countries such as the United States, Europe, and Japan, NIPT technology in China differs in three main aspects: testing platforms, regulatory pathways, and medical insurance coverage.

China has clear advantages in cost control and widespread application, but there is room for improvement in genetic counseling support and follow-up systems for positive cases. The American College of Obstetricians and Gynecologists (ACOG) explicitly recommends that all pregnant women, regardless of age, should be informed of the option for NIPT. China's "Technical Specifications for Prenatal Screening" places greater emphasis on managing the appropriate population to avoid overuse.

Applicable and Non-Applicable Populations

Suitable Candidates for NIPT

• Maternal age at delivery ≥35 years, but who decline or are not suitable for invasive prenatal diagnosis;
• Serological screening (maternal serum screening) results indicate borderline risk or a single abnormal marker;
• Ultrasound suggests soft markers for fetal abnormalities (e.g., increased nuchal translucency, absent nasal bone) but does not meet criteria for amniocentesis;
• History of a previous pregnancy with chromosomal abnormality, but unwilling to undergo repeat invasive testing in the current pregnancy;
• Pregnancies resulting from assisted reproductive technology (in vitro fertilization-embryo transfer), especially singleton pregnancies;
• Maternal carrier of a chromosomal structural abnormality (requires evaluation after genetic counseling).

Unsuitable or Requiring Careful Evaluation

• Gestational age <12 weeks (insufficient fetal fraction, increased risk of false negatives);
• Twin or multiple pregnancies (decreased accuracy, especially for triplets or more);
• Maternal BMI ≥30 (reduced proportion of fetal fraction in peripheral blood);
• Received allogeneic blood transfusion, transplant, or immunotherapy within the last 3 months;
• Maternal active malignancy (may interfere with the source determination of cell-free DNA);
• History of a previous pregnancy with chromosomal abnormality and refusal of subsequent invasive diagnosis in the current pregnancy (NIPT alone is not recommended).

Actual Testing Process

The entire NIPT testing process involves four stages: clinical consultation, blood collection, laboratory analysis, and result interpretation. The standard turnaround time is 7–14 working days.

1. Genetic Counseling: The doctor evaluates indications, explains the difference between screening and diagnosis, and obtains informed consent.
2. Information Collection: Records gestational age (confirmed by ultrasound), BMI, pregnancy method, obstetric history, and family genetic history.
3. Venipuncture: Draws 8–10 ml of peripheral blood; fasting is not required, and blood draw should avoid vigorous exercise beforehand.
4. Laboratory Testing: Plasma separation, cell-free DNA extraction, library construction, high-throughput sequencing, and bioinformatics analysis.
5. Result Issuance: Provides a report indicating "low risk" or "high risk," along with testing notes and recommendations.
6. Result Interpretation: The doctor provides follow-up recommendations based on clinical information—routine prenatal care for low-risk results; referral to a prenatal diagnosis center for high-risk results.

Key parameters to focus on in the test report include: fetal fraction (should be ≥4%), Z-score (test value for each chromosome, normal range -3 to +3), and test indication (e.g., "high risk for trisomy 21" or "indication of sex chromosome abnormality").

Easily Overlooked Details

In clinical practice, the following factors are often overlooked but can directly lead to test failure or result deviation:

• Fetal fraction is influenced by multiple factors: The smaller the gestational age, the higher the BMI, and the smaller the placental volume, the lower the fetal fraction. When fetal fraction is <4%, the test failure rate can reach 5%–10%.
• One abnormal twin may be masked: If one twin has trisomy 21 and the other is normal, the mixture of cell-free DNA proportions may lead to a false negative or an inconclusive result.
• Recent immunization or infection: Activation of the maternal immune system may cause fluctuations in the proportion of maternal components in cell-free DNA, affecting analysis.
• Use of anticoagulant medications: Anticoagulants such as low molecular weight heparin may affect PCR amplification efficiency but are not an absolute contraindication.
• Report turnaround time affected by logistics: Longer transport times for specimens from remote areas may lead to degradation of cell-free DNA in plasma; the time from blood draw to processing should be ≤72 hours.

Most Common Pitfalls

Based on clinical feedback, the following three scenarios are where patients and some primary care doctors are most prone to cognitive biases:

① "Low risk" equals "no problem"
A low-risk NIPT result only indicates a very low probability of the target chromosomal abnormalities, but does not rule out other chromosomal structural abnormalities, single-gene disorders, or small microdeletions. Some patients may therefore neglect systematic ultrasound screening, missing the opportunity to detect structural anomalies.

② "High risk" directly leads to termination of pregnancy
Making a decision to terminate a pregnancy based solely on a high-risk NIPT result without confirmation via amniocentesis or chorionic villus sampling carries a risk of misdiagnosis. This is especially true for high-risk sex chromosome results, where the positive predictive value is only 15%–40%, meaning most high-risk results are not actually abnormal upon confirmation.

③ Ignoring the testing window
The NIPT testing window is 12–22⁺⁶ weeks of gestation. Beyond 22⁺⁶ weeks, the fetal fraction may decrease, and the time window for subsequent invasive diagnosis and pregnancy decision-making becomes insufficient. Some pregnant women decide to test in the second or third trimester, only to receive results near or after the intervention deadline.

Frequently Asked Questions

Q1: Which is more accurate, NIPT or amniocentesis?

Amniocentesis is the diagnostic gold standard, with an accuracy rate >99.9%, capable of detecting all chromosomal numerical and structural abnormalities. NIPT is a screening technology; its accuracy varies depending on the target chromosome. It approaches diagnostic levels for trisomy 21 but has limited accuracy for other chromosomal abnormalities. The two cannot replace each other.

Q2: How much does NIPT cost? Is it covered by medical insurance?

The cost of NIPT in China ranges from approximately 1000 to 3000 RMB. Some provinces and cities (e.g., Beijing, Shenzhen, Zhejiang) have included it in medical insurance or local financial subsidies. The specific reimbursement rate varies by regional policy. Cell-free fetal DNA screening for embryos (NI-PGT) conducted by assisted reproductive centers is currently a self-pay item, costing approximately 3000–6000 RMB.

Q3: If NIPT results are high risk, will the child definitely have a problem?

Not necessarily. The positive predictive value for trisomy 21 is 80%–95%, meaning approximately 5%–20% of high-risk results are confirmed as false positives by amniocentesis. The proportion of false positives is even higher for high-risk sex chromosome results. Confirmation through invasive diagnosis is essential.

Q4: Is there a difference between NIPT for IVF pregnancies and natural pregnancies?

It is essentially the same, but for IVF pregnancies, note that gestational age is calculated from the embryo transfer date, not the last menstrual period. Some studies suggest that the fetal fraction in IVF pregnancies may be slightly lower than in natural pregnancies, but this is not associated with clinical outcomes. Embryo non-invasive screening (NI-PGT) is similar in principle to prenatal NIPT but belongs to a different application scenario and should not be used interchangeably.

Q5: Can NIPT detect all chromosomal abnormalities?

No. NIPT primarily targets numerical abnormalities of entire chromosomes (aneuploidy). It cannot detect balanced translocations, inversions, uniparental disomy, small deletions/duplications (<10 Mb), or single-gene mutations. For microdeletion syndromes, a specific expanded NIPT (NIPT-plus) must be selected, but its positive predictive value remains low.

Doctor's Recommendations

From the clinical practice of reproductive medicine and prenatal diagnosis, regarding the question "How is non-invasive chromosomal screening in China?", the following recommendations are offered:

• View NIPT as a high-precision screening, not a diagnosis. Any NIPT result must be interpreted in the context of genetic counseling; high-risk results require invasive confirmation.
• Choose accredited testing facilities. Ensure the laboratory passes the external quality assessment of the National Center for Clinical Laboratories, with traceable data quality.
• Use in conjunction with ultrasound screening. NIPT cannot replace mid-trimester systematic ultrasound; the two complement each other to cover major structural and chromosomal abnormalities.
• Pay attention to fetal fraction and testing platform. Fetal fraction directly affects accuracy; if below 4%, consider a repeat blood draw or alternative options.
• Be rational about "expanded" testing. Although NIPT-plus can screen for microdeletions, its positive predictive value is generally low; choose it after full informed consent.