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Tan Xiaojun
·Senior reproductive medicine expert
·Postdoctoral fellow at Peking University
·PhD candidate at Xiangya School of Medicine, Central South
University
·Master’s tutor at Central South University
· Master's degree candidate in reproductive
medicine at the University of South China
· Professional training at Huazhong University
of Science and Technology and Tongji
Hospital Reproductive Center
Expertise:
diagnosis and treatment of infertility, first/second/third generation IVF (including
egg/sperm donation), microsperm retrieval, embryo freezing and resuscitation, artificial
insemination (including husband's sperm and sperm donation), paternity testing, chromosomal
disease
diagnosis, high-throughput gene sequencing, endometrial receptivity gene testing and other
clinical
technology applications. Many of these technologies are at the leading level both domestically
and
internationally.
How to choose a second child for pregnancy? Understand PGT-A and PGT-M, which is closer to your medical indications?
Let's take apart the core question first: Are you choosing "technology" or "risk management path"?
Many people ask "PGT-A or PGT-M is more suitable for second-child pregnancy". On the surface, they are choosing one from the other, but in essence, they are judging: this pregnancy is mainly to solve the risk of abnormal chromosome number of embryos or the risk of transmission of single-gene genetic diseases known in the family.
Let's start with the conclusion: If one or both of the husband and wife are known to carry a definite disease-causing gene mutation, or there is a definite single-gene genetic disease clue in the first child and family members, PGT-M is usually given priority; If the risk of monogenic disease is not clear, but there are old age, repeated abortion, repeated implantation failure, etc., it is more common to discuss whether PGT-A has indications in clinic. * * These two technologies are not "who is more advanced", but solve different problems. Both ASRM and ESHRE classify PGT into different subtypes, among which PGT-A is aimed at embryo aneuploidy and PGT-M is aimed at monogenic diseases, with different indications, detection targets and preliminary preparation.
How to distinguish technology? Don't mix PGT-A and PGT-M into one thing yet.
The focus of PGT-A is to see if there is an abnormal chromosome number in the embryo, which is often called aneuploidy. HFEA classifies it as an additional item for embryo detection, which is mainly used to identify embryos with abnormal chromosome number. However, whether it can improve the outcome of live births is not consistent for everyone, so it cannot be understood as "it is easier to succeed if you do it." The ASRM 2024 opinion also emphasizes that the clinical benefit of PGT-A needs to be judged in combination with specific population, rather than generalized to all test-tube patients.
PGT-M, on the other hand, is aimed at specific single-gene genetic diseases, such as certain thalassemia, spinal muscular atrophy, cystic fibrosis and other types of genetic risks. Its premise is not "age", but "whether there is a clear genetic target". ASRM 2023 pointed out that PGT-M is mainly used to identify whether embryos carry specific pathogenic variation; ESHRE also listed PGT-M as an independent technology path. According to the published information of HFEA in Britain, PGT-M can be used to avoid transmitting a large number of approved monogenic diseases.
Expert tip: PGT-A cannot replace PGT-M.
If there is a clear genetic risk of single gene in the family, only PGT-A may not answer the core question "Does this embryo carry the disease-causing gene?". On the contrary, when there is no clear evidence of monogenic disease, there is usually no medical basis for directly going to PGT-M.
Which second-child families need to give priority to PGT-M?
If the first child has been diagnosed with a genetic disease, or the genetic test of both husband and wife suggests that they carry the same recessive genetic disease-related variation, or one of them carries the dominant genetic disease-related variation, then when the second child is pregnant, PGT-M is often not a question of "whether to do it or not", but is closer to the precise risk avoidance tool. In such cases, the clinical concern is to "avoid transmitting the known diseases to the next generation", rather than simply improving the implantation rate.
The advantages of this group of people are clear: clear goals, clear targets for detection, and relatively closed-loop decision logic.
However, the risks should also be made clear: PGT-M usually needs more adequate preliminary data preparation, and some cases need family verification, probe or linkage analysis design first, and the cycle may be more complicated; At the same time, it solves the risk of specific monogenic diseases, which does not mean that all chromosome problems and pregnancy problems are solved at one time.
Which second-child families will discuss PGT-A?
If there is no clear background of monogenic diseases, but there are cases of aging, repeated abortion in the past, repeated implantation of embryos, and unsatisfactory quality of embryos in the past, PGT-A is often included in the discussion. Because the risk of embryo aneuploidy increases with the increase of maternal age, which is a common fact in reproductive medicine. However, "negotiable" does not mean "everyone should do it". HFEA clearly suggests that the current evidence does not support PGT-A as a general gain item that is effective for most patients.
Its advantages are: in a specific population, it may help to screen out embryos with more normal chromosome numbers and optimize the transfer decision.
Its disadvantages are also very realistic: it cannot guarantee a live birth; All genetic and developmental problems cannot be ruled out; And for people with a small number of embryos, the number of transplantable embryos may be further reduced after screening. The attitude of ASRM 2024 document towards PGT-A is essentially four words: choose carefully.
Expert tip: PGT-A is more like a "layered tool" than a "successful commitment".
Whether to do PGT-A depends on embryo reserve, time cost and transplantation strategy for people who are already few and older but have limited eggs, and cannot be mechanically applied.
What's the difference in process? Many people neglect the preparation stage.
From the test tube process, both of them are common in promoting ovulation, taking eggs, in vitro fertilization, biopsy after embryo culture to blastocyst stage, and then send them for inspection, and then decide the transplantation strategy according to the results. ESHRE's PGT proposal has a clear framework for tissue management, embryo biopsy and detection process.
But the real difference often appears in the early stage.
PGT-M often needs to confirm the pathogenic variation and sort out the family data first, and some centers will prepare more complicated detection schemes. PGT-A focuses more on chromosome number analysis of embryos. That is to say, the prophase of PGT-M pays more attention to "cause confirmation" and the prophase of PGT-A pays more attention to "crowd assessment".
Frequently asked questions: Four things that are most likely to be wrong when preparing for a second child.
The first child is healthy, so the second child doesn't need to consider PGT-M?
Not necessarily. If a definite genetic disease is later found in the family, or if the husband and wife confirm the risk of carrying it after testing, the second child may still have PGT-M indications. The key is to look at genetic evidence, not "whether the surface of the last fetus is normal".
Is PGT-A suitable for all elderly women?
No. Old age is one of the discussion factors, but it is not an automatic indication. Whether it is worth doing should be judged together with the number of embryos, the history of abortion and the outcome of previous test tubes.
Can PGT-A and PGT-M do it together?
Some clinical scenarios can be considered jointly, but the premise is that there are corresponding medical needs at the same time. It is not that the more you do, the better, but that the problems should be corresponding.
Does PGT mean that children must be fine?
Can't understand it like this. Any PGT has a detection boundary, and the pregnancy outcome is also affected by uterine environment, embryonic development potential, endocrine and pregnancy factors.
Summary: How to choose a second child for pregnancy?
If your core risk is "whether a known genetic disease will be transmitted to a second child", discuss PGT-M first.
If your core risk is "the embryo chromosome abnormality behind age, abortion and repeated failure", you will enter the discussion scope of PGT-A.
If both types of risks exist, the reproductive doctor and the genetic consulting team should evaluate whether a combination strategy is needed.
From the first-principles point of view, the second pregnancy preparation is not to "choose the more advanced one" between PGT-A and PGT-M, but to match the known risk types with the capability boundary of detection tools.
Common aliases:Kyrgyzstan Tulip Reproductive Center, Tulip IVF, Tulip Reproductive Center, Tulip Hospital, Kyrgyz Tulip Reproductive Center, Kyrgyz Tulip Hospital
