Still struggling with Tang sieve, non-invasive, sheep wear how to choose? This article tells you all about it

Different situations have different choices!

Down Syndrome (DS) is Trisomy 21, also known as congenital stupidity, the most common chromosomal abnormality, caused by the addition of one more chromosome 21.

Down syndrome is usually an occasional chromosomal disorder, and even if both husband and wife have normal chromosomes, it is still possible to have a child with Down syndrome.

Pregnant women of all ages have the possibility of having a Down child, and pregnant women of advanced age (especially over 35 years old) are at increased risk of having a child with Down syndrome, and the older they are, the higher the risk.

The incidence of Down syndrome is about 1/600 to 1/800, and in mainland China, for example, about one Down child is born every 20 minutes. 60% of Down's children are miscarried during the fetal period, and the survivors show moderate to severe mental retardation and physical abnormalities, and often carry multi-system complications, and cannot fully take care of themselves, causing serious mental and economic burdens to the children's families and society.

So far, Down syndrome is still incurable, and the treatment is mainly for some complications of Down syndrome: congenital heart disease, hearing impairment, leukemia, thyroid disease, etc.

Finding high-risk groups through pregnancy screening, recommending that high-risk groups undergo prenatal diagnosis and diagnosis, early detection and timely termination of pregnancy, and avoiding the birth of such children are important secondary prevention measures for preventing birth defects in mainland China.

Therefore, pregnant mothers need to clarify a point of view:

Prenatal screening≠ prenatal screening ≠ prenatal diagnosis

※ Prenatal examination: More attention is paid to the mother's health and the baby's growth and development.

Prenatal screening and prenatal diagnosis focus on birth defects such as genetic diseases in babies.

※Prenatal screening: Through a simple, economical, and less traumatic method, high-risk pregnant women with congenital defects and genetic diseases are found from the pregnant women population to further clarify the diagnosis.

Screening methods include Tang screening, noninvasive DNA, imaging methods, etc.

※ Prenatal diagnosis: Diagnosis of congenital defects and genetic diseases of the fetus. Methods for obtaining fetal cells include amniocentesis, villus sampling, umbilical vein puncture, etc., and diagnostic methods include cytogenetics, molecular genetics, biochemical immunity, imaging methods, etc.

Tang screening (i.e., prenatal screening for Down syndrome)

1. Concept

The peripheral blood of pregnant women is drawn, some biochemical indicators in the serum are detected, and the risk of fetal development of Down syndrome (trisomy 21), Edward's syndrome (trisomy 18) and open neural tube defects is calculated by combining the age, gestational age, and weight of pregnant women.

2. Classification

According to the gestational period at the time of blood collection, it is divided into early Tang sieve (9 to 13 + 6 weeks) and intermediate Tang sieve (15 ~ 20 + 6 weeks), and the middle Tang sieve is divided into two, three and quadruple screening according to the serological indicators detected.

3. Recommendation index

Combined early-to-mid-pregnancy screening> first-trimester Tang screening (NT + serum studentization index) (especially suitable for twins) > second trimester quadruple screening> second trimester triple screening> second trimester secondary screening.

4. Result processing

A high-risk outcome of trisomy 21 or trisomy 18 is recommended for prenatal diagnosis i.e., amniocentesis;

Open neural tube defects are at high risk and ultrasound prenatal diagnosis is recommended. A trisomy 21 or trisomy 18 results of critical risk are recommended for noninvasive DNA prenatal testing.

If it is low-risk, routine obstetric examination is recommended.

5. Advantages

※ Operability: Strong, only 2-3ml of pregnant women's peripheral blood need to be drawn.

※Test time limit: It can be tested in the early pregnancy. Early sieve: 9 to 13+ 6 weeks, medium sieve: 15 to 20 + 6 weeks.

※Price: The lowest of the three.

※Reporting time: Short.

6. Limitations

※ It is not safe not to do screening, but it is also not safe to screen at low risk

In layman's terms: when the detection rate is 75%, 1/4 of the fetuses with Down syndrome are still hidden in the low-risk pregnant women of Tang Screening.

※ High risk does not dare not do amniocentesis, but most of them are normal

In layman's terms: 50 out of every 1,000 pregnant women who do Down screening are rated as high risk, 50 high-risk pregnant women with Tang screening are prenatally diagnosed with about 1 pregnant woman who is diagnosed with a Down child, and the remaining 49 are false alarms.

※There are many factors affecting risk assessment, and quality control is difficult

Noninvasive DNA prenatal testing

That is, prenatal detection of fetal free DNA in pregnant women's peripheral blood.

1. Concept

The peripheral blood of pregnant women was drawn, the free DNA of the fetus in the maternal peripheral plasma was sequenced by next-generation DNA sequencing technology, and the sequencing results were bioinformatic analysis to obtain the risk of chromosomal aneuploidy disease (trisomy 21, trisomy 18, trisomy 13).

2. Advantages

More accurate than tang sieves, safer than sheep to wear.

※ Operability: Strong, only 10ml of pregnant women's peripheral blood needs to be drawn.

※Test time limit: more than 12 weeks of pregnancy can be tested, the appropriate gestational week is 12 ~ 22 + 6 weeks.

※Reporting time: Shorter.

3. Limitations

※Price: More expensive

※Detection scope: At present, only trisomy 21-, trisomy 18, and trisomy 13 are detected, and 23 pairs of chromosomes cannot be completely covered.

4. Especially suitable

※Pregnant women who intend to undergo Tang screening and the economic conditions are permitting.

※ Pregnant women who missed the Tang sieve.

※ Tang sieving critical risk of pregnant women.

※Pregnant women with contraindications to interventional prenatal diagnosis (e.g., aura preterm birth, fever, bleeding, unhealed infection, etc.).

※Pregnant women who are extremely anxious about amniocentesis.

5, more suitable

※ Tang screening high-risk pregnant women: the risk level is less than 1/50.

※Advanced maternal age: 35 to 38 years old.

※Pregnant women with twin pregnancies.

Special reminder: It is recommended to be fully informed by a genetic counselor or obstetrician.

amniocentesis

1. Concept

Usually referred to as sheep puncture or amniocentesis refers to amniocentesis, which is a technique of pumping amniotic fluid through the abdominal wall, uterine muscle layer and amniotic membrane through the abdominal wall, uterine muscle layer and amniotic membrane under ultrasound positioning or guidance.

By extracting about 20 ml of amniotic fluid, the fetal exfoliation cells in the amniotic fluid are obtained, and then these cells are used to diagnose whether the fetus has some congenital diseases.

2. Advantages

※Status: The "gold standard" for the diagnosis of fetal chromosomal diseases.

※Detection range: It can detect abnormalities in the number of chromosomes in all fetuses and abnormalities in the structure of large segments of chromosomes.

※Test time limit: long, the appropriate gestational age of testing is 18 to 22 + 6 weeks.

3. Limitations

※There is a risk of miscarriage: The miscarriage rate is about 0.2% to 0.5%.

※Influencing factors: There is a possibility that cell culture fails and results cannot be obtained.

※Report time: Long.

4. Who should choose sheep to wear?

※ Pregnant women with a due date of birth age greater than 35 years (increased incidence of Down syndrome and other chromosomal abnormalities, especially over 38 years);

※Prenatal screening of high-risk groups (especially the high risk of noninvasive DNA testing, the risk of Tang screening is more than 1/50, the NT > during early pregnancy is 3.5mm, etc.);

※Pregnant women who have given birth to a child with chromosomal disease;

※Pregnant women who are suspected of having chromosomal diseases in prenatal examination (such as ultrasound suggesting fetal structural malformations, intrauterine growth retardation, etc.);

※One of the spouses is a carrier of chromosomal abnormalities;

※ Pregnant women may be carriers of X-linked genetic disease genes;

※Others: Those who have a history of adverse pregnancy or contact with special teratogenic factors.

4. Contraindications to puncture

※Those who have not cured preoperative infection or who are infected on the day of surgery and may be infected.

※There is bleeding in the central placenta previa or placenta previa or low placenta.

※Those who have not healed the threatened miscarriage.

Special reminder: It is recommended to be fully informed by a genetic counselor or obstetrician.

To summarize:

As a project to evaluate and diagnose Tang's children, Tang sieve, non-invasive, and sheep wear have their own advantages and disadvantages.

Tang sieve penetration rate is high, the price is cheap, but the accuracy rate is relatively low.

Non-invasive DNA accuracy is high, safe and reliable, and pregnant mothers with economic conditions can choose from.

Amniocentesis is recommended for high-risk individuals.

With the improvement of the level of medical care, pre-pregnancy eugenic examination, prenatal screening and prenatal diagnosis have become an important means of preventing birth defects, which can effectively reduce the occurrence of birth defects, is a low-cost and high-efficiency preventive measure, and is of great significance to improving the quality of the birth population.