How to choose between non-invasive DNA testing and amniocentesis? Non-invasive DNA is a prenatal testing technology developed in recent years, abbreviated as NIPT (Non-invasivePrenatalTesting), which has the characteristics of non-invasive sampling, no risk of miscarriage, high sensitivity and high accuracy, and therefore is rapidly gaining popularity among mothers and fathers-to-be. However, due to technical limitations, NIPT is not suitable for all pregnant women, and if not used properly, it may also bring negative effects. What are the main differences between NIPT and traditional invasive prenatal diagnostic techniques? The following author introduces the main features of the two types of technologies, hoping that you can choose the right prenatal screening method to avoid following the trend and blindly following. Traditional invasive prenatal diagnostic techniques include: chorionic villus sampling, amniocentesis and umbilical cord blood sampling. Clinically, amniocentesis is the most widely used, usually in the middle of pregnancy, under real-time ultrasound monitoring, a fine needle is inserted through the abdomen and 20 ml of amniotic fluid is extracted after entering the amniotic cavity. The fetal chromosomes are then cultured for 2 weeks and specially processed to obtain fetal chromosomes for karyotype analysis. Because the fine needle has to enter the amniotic cavity, it may lead to complications such as miscarriage and infection, among which miscarriage is more common. The incidence of miscarriage after puncture is about 3 per 1,000, and this probability is not only related to the physical condition of the pregnant woman and her gestational week, but also to the experience of the puncturing doctor and ultrasonographer. To minimize the occurrence of miscarriage after amniocentesis, the surgeon will take a detailed history and perform the necessary preoperative tests before the puncture. The following conditions may lead to an increased risk of miscarriage: 1) suspected contractions prior to puncture; 2) small amount of vaginal bleeding prior to puncture; 3) history of recurrent spontaneous miscarriage; 4) combined uterine fibroids in pregnancy; 5) large month puncture, especially at ≥25 weeks gestation; 6) twin pregnancies. Because whether or not to miscarry after amniocentesis is related to the pregnant woman’s own condition, gestational week and doctor’s experience, it is recommended that pregnant women who undergo amniocentesis should try to have the procedure in their own good condition, at a suitable gestational week (preferably 18-22 weeks), and choose a hospital with prenatal diagnosis qualification and experience in puncture, especially to remind mothers-to-be that there is prenatal diagnosis qualification ≠ real-time ultrasound monitoring, and some hospitals may arrange the procedure on the day of the procedure due to Some hospitals may arrange for ultrasound examination on the day of surgery due to staffing problems, and then perform another amniocentesis after positioning, which may reduce the safety of the procedure. NIPT is a technique that uses the blood of the pregnant woman as the test specimen without entering the amniotic cavity at all. in 1997, scientists discovered fetal free DNA fragments in the blood of pregnant women. although this was a remarkable discovery, the amount of fetal DNA in the mother’s blood was so small that previous testing techniques were unable to test such a small sample and draw definitive conclusions. The recent development of high-throughput genetic sequencing technology has made non-invasive prenatal testing possible, using which tiny fragments of fetal DNA in maternal blood can be sequenced and the results analyzed for bioinformatics to detect the presence of the three major chromosomal disorders in the fetus. In addition, the test can be performed from 12 weeks of gestation. Therefore, compared with amniocentesis, the biggest advantage of NIPT is the safety of sampling and early detection, which brings great benefits to those pregnant women who are not suitable for amniocentesis. Second, the difference in diagnostic scope and accuracy Since NIPT is very safe, can it replace karyotyping? The answer is no. The final karyotype analysis report issued after amniocentesis covers 23 pairs of chromosomes, which can tell the number of chromosomal abnormalities (most commonly trisomy 21, trisomy 18, trisomy 13) and also diagnose structural abnormalities, such as balanced translocation, unbalanced structural abnormalities, marker chromosomes, etc. Therefore, the diagnostic scope is very wide and basically covers all chromosomal diseases. In contrast, the detection range of NIPT is much smaller, and the technique can only detect the three most common chromosomal diseases, namely trisomy 21, trisomy 18, and trisomy 13, with detection rates of 99%, 96.8%, and 92.1%, respectively. Despite the very high detection rates, there are still very few missed detections, while structural abnormalities or genetic lesions, such as micro-repeats and microdeletions, cannot be detected, therefore NIPT can detect very limited diseases and its clinical application is screening in nature, except that its accuracy is much higher than serological screening, whereas amniocentesis is applied as a prenatal diagnostic technique and is still recognized as the gold standard for prenatal diagnosis of chromosomal disorders. Another issue of concern is the accuracy of the test. A review of most of the literature and scientific articles will lead to the conclusion that karyotype analysis and NIPT have comparable accuracy rates. In other words, if the mother-to-be gets a NIPT report and the conclusion is “low risk for trisomy 21, low risk for trisomy 18, low risk for trisomy 13”, it means that there is a 99% chance that the baby is not trisomy 21 or trisomy 18 or trisomy 13; if the mother-to-be gets an amniocentesis report and the conclusion is “no significant karyotype abnormalities seen If the mother-to-be gets an amniocentesis report that concludes “no significant karyotype abnormalities”, that means there is a 99% chance that the baby does not have a chromosomal disorder and a 100% chance that the baby does not have trisomy 21 or trisomy 18 or trisomy 13, which is a very big difference. Although the accuracy of NIPT is quite high, it is still impossible to avoid false positive and false negative results under the current conditions. For false positive reports, usually another amniocentesis can solve the problem, while false negative results may lead to the birth of a Down’s child, bringing pain to the family and the affected child. Once the ultrasound indicates abnormalities, it is still necessary to perform amniocentesis in order to avoid the negative impact of false negative NIPT results. NIPT is suitable for all pregnant women who wish to exclude common fetal chromosomal disorders due to its safety and early stage; all pregnant women with high risk of serum screening in early and mid pregnancy; all pregnant women who need fetal chromosome examination but have contraindications to amniocentesis, including: central placenta praevia, RH negative blood type, abnormal coagulation function, pre-eclampsia, history of recurrent spontaneous miscarriage, etc. However, due to the narrow scope of the test, the following pregnant women who may have other chromosomal abnormalities need to be used with caution: pregnant women in which one of the spouses has a chromosomal disorder or has had a pregnancy or child with a chromosomal disorder; pregnant women of advanced age ≥35 years old; pregnant women with abnormalities detected by ultrasound malformation screening; amniocentesis is indicated for the following groups: all mid-trimester pregnant women who wish to obtain a definitive diagnosis of fetal chromosomes and have no contraindications to puncture; early and mid-trimester pregnant women The following groups of people are suitable for amniocentesis: all pregnant women in mid-term pregnancy who wish to obtain a definite diagnosis of chromosomes and have no contraindication for puncture; pregnant women with high risk of serum screening; pregnant women of advanced age ≥35 years old; pregnant women with chromosomal disease in one of the spouses or who have had a pregnancy or child with chromosomal disease; pregnant women with abnormalities detected by ultrasound malformation screening; pregnant women with abnormalities detected; in summary, NIPT has the characteristics of safety, high detection rate, high accuracy and narrow detection range, while amniocentesis has the advantages of high detection rate and high accuracy, and its detection In addition to the advantages of high detection rate and accuracy, NIPT has a wide range of detection, including not only all chromosomal diseases, but also genetic defects, but there is a risk of miscarriage or infection. Every mother and father-to-be should make a choice after weighing the pros and cons, and should not blindly follow the trend, while for precious children such as twin pregnancies and IVF pregnancies, we prefer NIPT, but of course, the interpretation of the report needs to be more careful and rigorous, and amniocentesis should be performed to help confirm the diagnosis if necessary.