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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.
Is PGT-A or PGT-M more suitable for polycystic ovary? PGT-A technical principle, PGT-M is suitable for people, assisted reproduction of polycystic ovary syndrome, comparison of embryo screening techniques, third-generation IVF process, chromosome aneuploidy screening, preimplantation detection of monogenic diseases.
Do polycystic ovary patients do PGT-A or PGT-M This technical comparison will help you clear your mind.
I. Technical definition: What problems do PGT-A and PGT-M solve respectively?
In the field of assisted reproduction, preimplantation genetic testing (PGT) is a general term for genetic screening or diagnosis before embryo transfer. According to different clinical needs, PGT is mainly divided into two directions: PGT-A and PGT-M.
PGT-A (preimplantation genetic testing for aneuploidy) is the screening of chromosome aneuploidy in embryos. This technique is used to detect whether there are abnormal chromosome numbers in embryos, such as trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome). PGT-A does not focus on specific pathogenic genes, but makes a global analysis of the copy number of all embryos.
PGT-M (preimplantation genetic testing for monogenic disorders) means preimplantation genetic testing of monogenic diseases. This technology is aimed at monogenic genetic diseases with defined pathogenic gene loci, such as cystic fibrosis, spinal muscular atrophy, thalassemia and so on. PGT-M needs to obtain the mutation information of pathogenic genes in the family first, and design a detection scheme for specific mutation sites.
Experts suggest that PGT-A and PGT-M are two completely different technical paths. The former solves the problem of "the number of chromosomes is right" and the latter solves the problem of "whether a specific gene has a pathogenic mutation". They are not mutually replaceable, and not all patients need to use them.
Second, the clinical application population: What kind of patients with polycystic ovary belong to?
Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disease in women of childbearing age. Epidemiological data show that the prevalence of PCOS in women of childbearing age is about 8%-13% (according to Rotterdam diagnostic criteria). The core features of PCOS patients include ovulation disorder, hyperandrogenism and polycystic ovarian changes.
The relationship between PGT-A and PCOS;
Clinical studies suggest that some offspring of PCOS patients may have an increased risk of chromosomal abnormalities. A study published in Human Reproduction shows that the aneuploidy rate of PCOS patients in blastocyst stage is higher than that of the control group, especially in the case of old age or insulin resistance. In addition, PCOS patients usually get more oocytes after ovulation induction, but there are individual differences in oocyte maturity and quality. Therefore, some reproductive medicine centers will recommend eligible PCOS patients to consider PGT-A screening to screen embryos with normal chromosomes for transplantation.
Relationship between PGT-M and PCOS;
PCOS itself is not caused by a single gene mutation, and its pathogenesis involves the interaction between multiple susceptible genes and environmental factors. At present, the known PCOS-related genes include FSHR, LHCGR, CYP17A1, INSR, etc., but the polymorphism of these genes does not conform to Mendel's genetic law and does not belong to the category of monogenic genetic diseases. Therefore, PCOS patients generally don't need PGT-M, unless the patient has a clearly pathogenic monogenic genetic disease mutation, or both husband and wife are carriers of the same autosomal recessive genetic disease.
Summary box:
PGT-A: It is suitable for PCOS complicated with old age, history of repeated abortion and previous history of embryo aneuploidy.
PGT-M: Not applicable to PCOS itself, only applicable to PCOS with monogenic disease carriers.
Comparison of technical processes: What are the differences between them in laboratory operation?
PGT-A standard process:
The fertilized eggs were obtained by conventional in vitro fertilization or intracytoplasmic sperm injection.
Embryo culture to blastocyst stage (day 5-6)
Biopsy of trophectoderm: take 3-5 cells from the outer layer of blastocyst.
Whole genome amplification and high-throughput sequencing (NGS)
Bioinformatics analysis to judge the variation of chromosome copy number
Screening aneuploid embryos for transplantation.
PGT-M standard process:
Pre-family verification: DNA samples of patients, spouses, parents or probands should be collected to complete linkage analysis or mutation site verification.
In vitro fertilization and embryo culture (same as PGT-A)
Biopsy of trophectoderm in blastocyst stage
After the whole genome is amplified, specific mutation sites are detected (commonly used methods include PCR- linkage analysis, SNP chip or NGS targeted sequencing).
Simultaneous screening of chromosome aneuploidy (some centers provide PGT-M+PGT-A combined detection)
Screening embryos without pathogenic mutation and normal chromosomes.
Time and cost difference:
PGT-A usually takes 4-6 weeks from biopsy to report.
PGT-M takes a long time to verify the previous family, and the total cycle is usually 8-12 weeks.
In terms of cost, PGT-M usually costs more than PGT-A because it needs individualized scheme design.
Fourth, the typical scenario of PCOS patients choosing PGT-A.
Scenario 1: PCOS with advanced age (≥38 years old)
Age is an independent risk factor for chromosome aneuploidy. The data show that the aneuploidy rate of women's embryos is about 40%-50% at the age of 38, and it can rise to 60%-70% at the age of 40. If PCOS patients are in the category of old age at the same time, the clinical value of PGT-A is clear.
Scenario 2: PCOS with repeated implantation failure or recurrent abortion
Some PCOS patients have a history of repeated embryo implantation failure or early pregnancy abortion. Clinical retrospective studies suggest that the abnormality of embryonic chromosomes is one of the important reasons in this kind of patients. PGT-A can help to screen aneuploid embryos, which can theoretically reduce the risk of abortion caused by chromosome abnormality of embryos.
Scenario 3: A large number of embryos are obtained after ovulation induction by PCOS, and the transfer order needs to be optimized.
PCOS patients often get more than 10 blastocysts in a single ovum retrieval cycle. In the case of a large number of embryos, PGT-A can provide quality information at chromosome level and assist clinical decision-making on the priority of embryo transfer.
Expert tip: PGT-A is not a "universal filter". It can't detect gene mutation, chromosome microdeletion and duplication (PGT-SR technique is needed), and it can't evaluate the epigenetic status of embryos. There is still the possibility of abortion or birth defects after the transfer of aneuploid embryos, and medical research shows that the risk is about 2%-5%.
V. Frequently asked questions: 7 questions that patients are most concerned about.
Question 1: Can 1：PCOS patients do PGT-A to improve the live birth rate?
A: The existing evidence-based medical evidence shows that PGT-A can reduce the abortion rate in a single transplantation cycle for PCOS patients who are old (over 35-40 years old) and can obtain multiple blastocysts, but the influence on the cumulative live birth rate is still controversial. Some randomized controlled trials suggest that the main advantages of PGT-A are to reduce invalid transplantation and shorten the time to live birth.
Q 2: Is it necessary for 2：PCOS to be PGT-M?
A: It is not necessary only because of PCOS diagnosis. PCOS is not a monogenic genetic disease, and there is no PGT-M test for PCOS "pathogenic gene" at present. If both husband and wife are carriers of the same autosomal recessive genetic disease (such as thalassemia, spinal muscular atrophy, etc.), PGT-M can be considered, which is not directly related to PCOS.
Q3: Can PGT-A and PGT-M be done at the same time?
A: Yes. Clinically, it is called "PGT-M+PGT-A combined detection", that is, while detecting specific gene mutations, the chromosome aneuploidy of embryos is analyzed simultaneously. It is suitable for patients with monogenic diseases and high risk of chromosomal abnormalities.
Q 4: Is the biopsy harmful to the embryo?
A: Biopsy of trophectoderm in blastocyst stage is recognized as a relatively safe operation at present. The data show that there is no statistically significant difference in the implantation rate of embryos after biopsy in experienced centers compared with those without biopsy. However, in theory, biopsy has potential effects on embryos, and clinical indications should be strictly controlled.
Q 5: Can PGT-A detect all genetic diseases?
A: No. PGT-A only detects chromosome number abnormalities and structural abnormalities of some large fragments (> ＞10-20Mb), but cannot detect monogenic diseases, mitochondrial diseases, polygenic diseases and epigenetic abnormalities.
Q 6: Can 6：PCOS patients not do PGT?
A: Yes. Most PCOS patients can obtain an acceptable pregnancy outcome through routine in vitro fertilization or intracytoplasmic sperm injection combined with morphological evaluation. PGT-A is an "additional screening technique" with clear medical indications, and not all PCOS patients must use it.
Question 7: Which institutions in China can do PGT?
A: By the end of 2023, there were more than 100 reproductive medicine centers with PGT qualification approved by the National Health and Wellness Committee, which were distributed in provincial capitals and some prefecture-level cities. Patients can check the access list of assisted reproductive technology published by the local health and wellness committee.
Six, decision-making process diagram
Step 1: Make clear your own diagnosis-have you diagnosed PCOS?
Step 2: Check whether it is combined with the status of carriers of monogenic diseases-it is recommended to carry out expanded carrier screening.
Step 3: Evaluate the age and birth history-is it ≥38 years old? Is there a history of ≥2 miscarriages or ≥3 implantation failures?
Step 4: If the carrier status of monogenic disease is merged → give priority to consulting PGT-M.
If there is no monogenic disease, but there is a history of old age or repeated abortion → the applicability of PGT-A can be evaluated.
If only PCOS has no other high risk factors → conventional in vitro fertilization may be enough.
VII. Summary: Look at the two technologies rationally and avoid excessive intervention.
Core conclusion:
It is more suitable for polycystic ovary to be PGT-A or PGT-M, and the answer depends on the specific clinical characteristics of patients. PCOS itself does not constitute an indication for PGT-M; PGT-A is suitable for some PCOS patients with advanced age, repeated abortion or high risk of embryo aneuploidy.
The selection of the two technologies should follow the principle of "medical necessity and informed consent" and avoid blindly adding testing items for "pursuing better results".
Advice to patients:
Complete systematic evaluation in reproductive medicine center, including karyotype analysis of both sides, carrier screening and ovarian reserve function test.
Fully discuss the benefits and limitations of different technical paths with reproductive doctors and genetic counselors.
It is clear that PGT technology can not "ensure the birth of healthy babies", but a tool to reduce specific genetic risks.
Make comprehensive decisions according to one's own economic conditions, time cost and psychological endurance.
Common aliases:Kyrgyzstan Tulip Reproductive Center, Tulip IVF, Tulip Reproductive Center, Tulip Hospital, Kyrgyz Tulip Reproductive Center, Kyrgyz Tulip Hospital
