Three generations of test tubes have been screened, do you still need to do amniocentesis?

Some mothers have a hard time conceiving a baby, have doubts about the amniocentesis test ordered by the doctor, and have already made a genetic diagnosis of the embryo before the transfer, so why should the baby be genetically diagnosed? Is it really necessary to do amniocentesis? What if the sheep wears a miscarriage? Today Xiaokang will help you explain this problem.

What is the difference between "Tang sieve", "non-invasive production sieve" and "amniotic puncture"?

First of all, let's distinguish the difference between the terms "Tang sieve", "non-invasive production sieve" and "amniocentesis", which are often placed in front of expectant mothers who do obstetric examinations.

"Tang screening" is to judge the risk of fetal Down syndrome and trisomy 18 syndrome by the peripheral blood serum biochemical index of pregnant women in the early and second trimesters of pregnancy, this traditional technique can greatly reduce the birth of children with Down syndrome, but the technology also has obvious limitations, such as high false positive rate and a certain missed test rate. That is to say, further amniocentesis of pregnant women who are "high-risk" found through "Tang screening" will find that most of them are normal; while "Tang screening" suggests that a certain proportion of children with Down syndrome are still born in the "low-risk" population.

"Non-invasive birth screening" is to determine the risk of fetal Down syndrome and other chromosomal abnormalities such as fetal Down syndrome by detecting fetal origin DNA in the peripheral blood of pregnant women after 12 weeks of pregnancy, the advantage of this technology is that the accuracy rate is high, the false positive rate is low, the missed test rate is low, and there is a trend to replace the traditional "Tang screening", the main problem is that the price is expensive.

"Amniocentesis" is the most commonly used material for prenatal diagnosis, at 18 to 22 weeks of pregnancy, under ultrasound guidance, puncture amniotic fluid samples for genetic testing, because the sampling is directly derived from the fetus, so it can be more accurate to directly reflect the chromosomes or genetic conditions of the fetus. The disadvantage is that invasive sampling is required and, while relatively safe, there is still a very low risk of miscarriage and infection.

"Tang screening" and "non-invasive birth screening" are all prenatal screening techniques, mainly to screen the fetus for the risk of chromosomal abnormal diseases, and the results of screening can only indicate the level of risk and cannot be diagnosed. "Amniocentesis" is the method of diagnosing the presence or absence of chromosomal disease in the fetus. If the "Tang screening" and "noninvasive DNA" tests indicate a high risk, further "amniocentesis" is required to confirm whether the fetus has a genetic disease.

For those pregnant women who are known to have a high risk of fetuses with hereditary diseases, they can skip the "Tang screening" or "non-invasive birth screening" and directly select the prenatal diagnosis of "amniocentesis" to exclude genetic diseases.

Is it still necessary to do three generations of test tubes to make sheep wear?

It should be emphasized that the "three-generation test tube" technology itself is not the reason why you need to do "amniocentesis", whether you need to do "amniocentesis", but also depends on what you do the "three-generation test tube".

1. For pregnant women who are pregnant after PGT-SR and PGT-M technology, it is recommended to choose "amniocentesis", because the risk of giving birth to chromosomal abnormalities and genetic defects in the couple is higher, although embryo testing has been done, but because the sample of embryo detection is very small, the detection technology is complex, there is a risk of misdiagnosis, it is recommended to choose "amniocentesis" as a means of further diagnosis to eliminate the risk of disease.

2. Pregnant women with PGT-A pregnancy can follow the principles and procedures of routine obstetric examination, do prenatal screening first, and if high-risk factors are found, "amniocentesis" is recommended. If you have chosen to transfer a "chimera" embryo in PGT-A, after obtaining pregnancy, it is also recommended to perform a direct "amniocentesis" to further exclude the risk of fetal chromosomal abnormalities.

In addition, non-invasive DNA testing (NYTPT) is currently a very popular test for pregnant mothers, it can make a more accurate screening of common chromosomal abnormalities such as trisomy 21, trisomy 18, trisomy 13, etc. For non-invasive DNA screening, if it is high risk, we still have to do amniocentesis later to further clarify the diagnosis, if it is low risk, even if the ultrasound is done later to check some structural deformities, we can not completely rule out the risk of giving birth to genetic defects. Therefore, for pregnant mothers with prenatal diagnostic indications, the doctor's preferred recommendation is amniocentesis.

Is the risk of amniocentesis high?

In fact, the risk of amniocentesis is exaggerated, which is a way of prenatal diagnosis, simple, safe and effective, after obtaining fetal samples through amniocentesis, it can prenatal diagnosis of fetal chromosomal diseases, genomic diseases, and single gene diseases (as needed) to minimize the risk of giving birth to children with severe genetic defects. In a formal institution, amniocentesis by an experienced doctor, the additional increase in the risk of miscarriage to the fetus is not more than one thousandth, this risk is very low, in fact, at 18-24 weeks, this period of time to do amniocentesis, even if the amniocente puncture is not done, there will be about 2% of the natural abortion risk, so relative to amniocentesis, it produces benefits, that is to say, we can obtain fetal cells, conduct fetal genetic diagnosis, avoid birth of severe defects, this risk is very low.

Amniocentesis is to collect fetal cells, for further genetic diagnosis, amniotic fluid cells it comes from amniotic membranes, fetal oral exfoliation cells, urinary tract exfoliation cells, skin exfoliation cells, relative to the placenta and umbilical cord blood, it is more representative of the fetus, it can be said to be the best prenatal diagnostic sample, through the amniotic fluid diagnosis we can find out whether the fetus has chromosomal diseases, genomic diseases, etc., then you can avoid giving birth to children with serious defects.

When is amniocentesis done?

Amniocentesis is generally done during 18-24 weeks, a week before the puncture needs to do blood draw, to do a preoperative examination, to check whether there are contraindications to amniocentesis, after puncture, our report time is based on our amniotic fluid after the test project, if it is some rapid molecular diagnosis, such as QF-PCR, or Bobs, etc., generally three days can get the report, but for conventional prenatal diagnosis, we are going to do chromosome karyotype and chromosome chip, Then this will take about four weeks.

epilogue

The above are some brief selection principles for common prenatal screening and diagnostic techniques, each pregnant woman's specific situation is also somewhat different, which test to choose, or need to individualize your prenatal consultation doctor to make the appropriate choice.