There is a new way to check pregnant women! On January 16, 2015, the National Health and Family Planning Commission announced the first batch of non-invasive genetic testing pilot units. Three units in Chongqing were approved, namely the First Affiliated Hospital of Chongqing Medical University, Southwest Hospital Affiliated to Third Military Medical University, and Chongqing Maternal and Child Health Hospital.
Yesterday, Huang Shuai, an obstetrician at the First Affiliated Hospital of Chongqing Medical University, told a Chongqing Evening News reporter that many pregnant women show high risk during Down syndrome screening (which checks whether the fetus is congenitally stupid), and after further examination, they often find nothing. In the past, amniocentesis was mostly used for diagnosis, which had a certain risk of miscarriage. It can now be partially replaced by non-invasive genetic testing.
Huang Shuai introduced that amniocentesis is to obtain information on the healthy development of the fetus by sampling amniotic fluid from pregnant women. Amniotic fluid cells are derived from fetal cells and have the same genetic information as the fetus. Non-invasive genetic testing only requires 5 ml of venous blood from pregnant women, and uses next-generation DNA sequencing technology to sequence cell-free DNA fragments (including fetal cell-free DNA) in the mother\’s peripheral plasma to obtain fetal genetic information and detect whether the fetus has three major chromosomal diseases. .
Huang Shuai introduced that non-invasive genetic testing is suitable for pregnant women over 35 years old who do not want to choose invasive prenatal diagnosis; pregnant women who do not want to choose invasive prenatal diagnosis because of high-risk screening results or single indicator value changes; due to increased fetal NT value Pregnant women with anatomical abnormalities or other anatomical abnormalities who are unwilling to choose invasive prenatal diagnosis; pregnant women who are not suitable for invasive prenatal diagnosis, such as virus carriers, placenta previa, low-lying placenta, oligohydramnios, negative RH blood type, and a history of miscarriage , threatened abortion or babies, etc.; pregnant women who have failed amniocentesis cell culture and are unwilling to accept or can no longer undergo invasive prenatal diagnosis; pregnant women who have positive serum screening and those who have psychological barriers to prenatal diagnosis.
It is reported that normal human cells contain 23 pairs (46) of chromosomes, including 22 pairs of autosomes and 1 pair of sex chromosomes that determine gender. Changes in the number of chromosomes, more or less than 46, and structural abnormalities can cause diseases, which are medically called chromosomal aneuploidy diseases. How to check before birth? How to choose the inspection method? According to Li Rong, a doctor at Chongqing Fetal Medicine Center, the screening scopes of various methods vary. Huang Shuai said: \”Non-invasive genetic testing can replace Down syndrome screening, but it cannot completely replace amniocentesis. No matter which method you choose, you should first ask your obstetrician to analyze whether it is suitable for you.\”
Down\’s screening
Scope of application: Screening for Down syndrome, also known as trisomy 21, which is congenital stupidity. Patients have one extra pair of chromosome 21 than normal people.
Advantages: Only venous blood is drawn, it is economical and costs 200 to 300 yuan.
Disadvantages: low detection rate and accuracy. Even the most comprehensive combined early and middle school screening can only detect 80% to 90% of children. High false positive rate, Down syndrome risk during screeningThe risk is high. After diagnosis, a large proportion are not.
Non-invasive genetic testing
Scope: Screens for common chromosomal aneuploidy disorders, including Down syndrome.
Advantages: Only venous blood is drawn, the detection rate is high, 99% of children can be detected, and the false positive rate is low.
Disadvantages: high cost, more than 2000~3000 yuan. Compared with amniocentesis, the detection range is slightly narrower and cannot see all fetal chromosomal information, and children with chromosomal structural abnormalities are rarely missed. Currently, the accuracy for chromosomes 21, 18, and 13 is relatively high, while the accuracy for sex chromosomes is slightly lower.
amniocentesis
Scope of application: In addition to the diagnosis of fetal chromosomal diseases, it can also be used to detect fetal metabolic diseases, fetal neural tube defects, fetal lung maturity and amniotic membrane infection.
Advantages: 46 chromosomes can be detected. With high accuracy, it is one of the prenatal diagnostic technologies with the widest detection range and the highest accuracy. It is especially suitable for pregnant mothers with high-risk factors such as abnormal birth history and family history.
Disadvantages: The comprehensive inspection costs about 1,500 yuan. There is a certain risk, the miscarriage rate is 0.5%. ~1%. In rare cases, cell culture fails and additional examination or re-puncture must be performed.