After preimplantation genetic testing (PGT), which is what our patients often call a three-generation test tube, is there no need for prenatal diagnosis? Or is it okay to do a non-invasive prenatal test (NIPT)?
The amniotic puncture that has been popularized by everyone in the past and everyone is actually not as terrible as everyone thinks, and the risk is also very low. However, as an invasive test, many mothers will still feel afraid from the heart, especially some older IVF mothers, so many times everyone chooses non-invasive prenatal testing.
However, for three generations of IVF mothers-to-be, doctors generally recommend amniocentesis instead of noninvasive DNA. Maybe you have to wonder again, obviously it is safer to draw blood than to draw amniotic fluid, why should you recommend doing amniocentesis? Today we continue to answer your questions.
Noninvasive prenatal testing, abbreviated as NIPT, is a prenatal screening technique that uses next-generation high-throughput sequencing to detect fetal chromosomal abnormalities. It is only necessary to sequence the free DNA fragments of the fetus in the maternal peripheral blood plasma by collecting the peripheral blood of pregnant women with a gestational age of 12-24 weeks, combined with biological information analysis, calculate the risk of fetal chromosomal aneuploidy, mainly detect trisomy 21, trisomy 18 and trisomy 13, and also indicate other chromosomal aneuploidy and chromosome deletions/duplications. However, this technique is of a screening nature, and if the test is high risk, it is still necessary to consider subsequent prenatal diagnosis to confirm the diagnosis.
In addition, NIPT currently cannot detect balanced chromosomal abnormalities, such as mutual translocations versus Robertson translocations; it cannot detect genetic disorders caused by genetic abnormalities.
Prenatal diagnosis refers to a means of diagnosing whether the fetus has a hereditary or congenital disease before the birth of the fetus, which has important clinical significance for the prevention and control of neonatal incidence.
At present, the methods of intrauterine prenatal diagnosis mainly include three categories: villous puncture in the first trimester of pregnancy, amniocentesis in the second trimester and umbilical vein puncture in the second and third trimesters of pregnancy. These techniques are mature and 99% accurate, but the disadvantage is that these extraction techniques are invasive, with a risk of miscarriage of 0.5-1% and a fetal teratogenic risk of 0.5-1%, and if karyotyping is performed, cell culture is required, and there is a possibility of culture failure. Therefore, it is mainly used clinically for prenatal diagnosis of high-risk groups (advanced age, positive serological screening, noninvasive screening suggests high-risk, single-gene disease PGT or chromosomal abnormalities PGT for pregnant pregnant women).
High-risk groups of natural pregnancy, the use of amniocentesis prenatal diagnostic techniques is easy to understand, why after three generations of test tubes, do you need prenatal diagnosis of amniocentesis?
This is actually a kind of double insurance.
The third-generation test tube is an exclusionary genetic test for the corresponding chromosomal abnormalities or known pathogenic gene mutations in the embryo before implantation into the uterus, which is a completely new technology, and only a small sample of embryonic cells (averaging 3-5 cells) is used for detection, the detection of future trophoblast cells that develop into a placenta, not the placental cells that develop into individuals, there may be chimeric conditions, the results can not be guaranteed to be 100% accurate, and there are misdiagnoses reported internationally. Although misdiagnosis is rare (two out of more than 70,000 embryos in our hospital), IVF is a precious child, and even a very low proportion of misdiagnosis needs to be ruled out.
Therefore, in the international and domestic industry standard operation process, it is stipulated that prenatal diagnosis needs to be checked again. In prenatal diagnosis, amniocentesis, although invasive, has the lowest risk of spontaneous abortion compared to villous puncture and umbilical vein puncture, and the technique is also the most mature. Therefore, for the third generation of IVF, doctors still recommend that pregnant women smoke amniotic fluid to prenatal diagnosis of the pregnant fetus.
This is the last guarantee against the misdiagnosis of three generations of IVF, do you know?
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