Preimplantation Genetic Diagnosis in Thailand: Technical Process, Indications, and Decision Points
Opening: Physician Decision Logic
In clinical reproductive medicine decision-making, the applicability of Preimplantation Genetic Testing (PGT) is typically based on three core elements: the patient's genetic risk level, embryo developmental potential, and laboratory testing capabilities. When considering Thailand as a destination, the integration of testing technology with domestic genetic counseling must also be evaluated. The following systematically reviews PGT in Thailand from the perspectives of technical classification, process arrangement, national differences, and clinical cases.
Module A + Module C combined1. Preimplantation Genetic Diagnosis in Thailand: Technical Classification and Indications
Preimplantation Genetic Diagnosis in Thailand (now collectively referred to as PGT) involves genetic testing of blastocysts formed through in vitro fertilization to select embryos that do not carry specific pathogenic genes or have normal chromosomes for transfer. Currently, Thailand primarily uses the Next-Generation Sequencing (NGS) platform, supplemented by SNP array technology, covering the following three types of testing.
| Test Type | Test Target | Indications |
|---|---|---|
| PGT-A | Chromosomal aneuploidy screening (Trisomy 21, Trisomy 18, Trisomy 13, sex chromosome number abnormalities, etc.) | Maternal age ≥38 years, recurrent implantation failure (≥2 times), recurrent miscarriage (≥2 times), previous aneuploidy pregnancy history |
| PGT-M | Monogenic disease testing (Thalassemia, Spinal Muscular Atrophy, Hereditary Deafness, Huntington's Disease, etc.) | One or both partners are known carriers or affected by a monogenic disease |
| PGT-SR | Chromosomal structural rearrangement testing (Balanced translocation, Robertsonian translocation, inversion, insertion, etc.) | One partner is a carrier of a chromosomal structural rearrangement, with a history of infertility or miscarriage |
Core Physician Decision Logic: PGT-A primarily addresses the question "Is the embryo's chromosome number correct?" PGT-M answers "Does it carry a specific pathogenic gene?" and PGT-SR targets "Are there structural problems with the chromosomes?" The technical pathways for the three types of testing differ, as do the requirements for the embryology laboratory, depth of genetic counseling, and pre-testing period. Some centers in Thailand can offer combined PGT-A+PGT-M testing, but PGT-M requires prior completion of family verification and probe design.
2. Technical Differences Between Thailand and Domestic PGT
PGT technology in Thailand and domestically differs in three main areas: regulatory pathways, testing scope, and laboratory standards. These differences directly impact the patient's process design and timeline.
| Comparison Dimension | Thailand | Mainland China |
|---|---|---|
| Regulatory Nature | Commercial medical practice, patient's autonomous choice, no strict indication restrictions | Approval system by the National Health Commission, must meet medical indications and have PGT qualification |
| PGT-A Scope | Applicable for advanced age, recurrent failure, miscarriage; some centers also accept "non-medical indication" sex selection (permitted by law in some countries) | Strictly limited to: maternal age ≥38 years, recurrent implantation failure ≥3 times, recurrent miscarriage ≥2 times, previous history of chromosomal abnormality pregnancy |
| PGT-M Disease Range | Depends on the gene panel design of the center's collaborating laboratory; some centers can test for 100+ monogenic diseases | Requires approval from the National Health Commission's genetic disease catalog; currently about 70-80 diseases can be tested, and must pass ethics committee review |
| Embryology Lab Certification | Some centers have JCI or ISO15189 certification, but there is no unified national PGT laboratory access standard | Must pass the National Health Commission's PGT technology access evaluation; the laboratory must have PCR lab qualifications and NGS platform certification |
| Genetic Counseling Requirements | Most centers offer genetic counseling in Chinese and English, but family verification and pre-testing must be completed by the patient domestically | Must be completed in a genetic counseling clinic with PGT qualifications; family verification is performed by the center's collaborating genetics laboratory |
From a clinical practice perspective, the "threshold" for PGT in Thailand is relatively flexible, but this means patients must take on more responsibility for complete genetic counseling and pre-testing. Domestic PGT access is stricter, but the process is highly standardized, and genetic counseling is more closely integrated with testing.
Module I + J: Actual Process and Timeline3. Complete PGT Process and Timeline in Thailand
The complete PGT process in Thailand is divided into a domestic preparation phase and a medical phase in Thailand, with an overall cycle of about 3 to 5 months. The following uses PGT-M (monogenic disease testing) as an example to illustrate the most complete process; steps for PGT-A and PGT-SR can be simplified accordingly.
Phase 1: Domestic Genetic Counseling and Pre-testing (1-2 months)
Genetic Counseling and Family Verification
Confirm the pathogenic gene locus, collect peripheral blood samples from the proband (affected family member) and both partners, and perform Sanger sequencing or WES validation. Thai laboratories require a clear pathogenic gene report and family linkage analysis results.
Probe Design and Pre-testing
Send family samples to the collaborating genetics laboratory in Thailand to design SNP linkage probes or PCR primers for the specific gene locus. The pre-testing period is typically 3 to 6 weeks; the PGT cycle can only proceed after successful completion.
Phase 2: Ovarian Stimulation and Embryo Culture in Thailand (Approximately 3-4 weeks)
Menstrual Cycle Initiation and Ovarian Stimulation
The woman arrives in Thailand on day 2-3 of her menstrual cycle. After ultrasound and hormone checks, an ovarian stimulation protocol is initiated, with an average stimulation duration of 10-12 days.
Egg Retrieval and ICSI Fertilization
Intracytoplasmic sperm injection (ICSI) is performed after egg retrieval to avoid DNA contamination from sperm affecting test accuracy.
Blastocyst Culture and Biopsy
Embryos are cultured to the blastocyst stage on day 5-6. 3-5 cells are biopsied from the trophectoderm, and the blastocyst is then cryopreserved.
Phase 3: Genetic Testing and Embryo Selection (2-4 weeks)
NGS Testing and Data Analysis
After whole genome amplification of the biopsied cells, NGS sequencing or SNP array analysis is performed to obtain information on chromosomal copy number variations (CNV) and single gene loci simultaneously.
Genetic Report Interpretation
The Thai laboratory issues a bilingual (Chinese and English) test report specifying the chromosome status and pathogenic gene carrier status for each embryo. The report should be reviewed by a domestic genetic physician.
Phase 4: Frozen Embryo Transfer (Approximately 2-3 weeks)
Endometrial Preparation and Transfer
Based on test results, a blastocyst with normal chromosomes and without the pathogenic gene is selected for transfer in a natural cycle or hormone replacement cycle.
Post-Transfer Luteal Support and Pregnancy Test
Blood is drawn for β-hCG testing 10-12 days after transfer to confirm pregnancy, and an ultrasound is performed on day 28 after transfer to confirm fetal heartbeat.
4. Cost Composition and Influencing Factors
The total cost of PGT in Thailand consists of several independent components. Price differences between centers are mainly reflected in embryo biopsy fees, testing platforms, and the depth of genetic counseling.
| Cost Item | Approximate Range (CNY) | Description |
|---|---|---|
| Genetic Counseling and Family Verification | 8,000 - 15,000 yuan | Completed domestically; some tertiary hospital genetic clinics may charge, or a third-party genetic company may be needed |
| Probe Design and Pre-testing | 12,000 - 25,000 yuan | Required only for PGT-M and PGT-SR; priced according to the number of loci and family complexity |
| Ovarian Stimulation and Egg Retrieval Surgery | 40,000 - 60,000 yuan | Includes medication, ultrasound monitoring, egg retrieval surgery, and anesthesia |
| ICSI Fertilization | 10,000 - 15,000 yuan | Standard single sperm injection fee |
| Blastocyst Culture and Biopsy | 18,000 - 25,000 yuan | Includes culture medium costs for blastocyst development and laser biopsy operation fee |
| Genetic Testing (NGS) | 15,000 - 25,000 yuan/embryo | Charged per embryo tested; some centers offer "embryo package prices" |
| Embryo Freezing and Storage | 8,000 - 12,000 yuan/year | Initial freezing fee includes first year storage fee |
| Frozen Embryo Transfer | 15,000 - 25,000 yuan | Includes endometrial preparation medication, transfer procedure, and luteal support |
Cost Variable: The number of embryos tested is the biggest variable. Testing 5 embryos versus 10 embryos can result in a difference of 20,000 to 30,000 yuan in testing fees. Some centers use a "single embryo flat fee" model for PGT-A, while PGT-M, due to the high cost of probe design and family verification, is typically 30% to 50% more expensive overall than PGT-A.
Module M: Clinical Case Scenario Analysis5. Clinical Case Scenario Analysis
The following three typical scenarios illustrate the application logic of PGT in Thailand in different clinical situations.
Scenario 1: Advanced Age with Recurrent Miscarriage
Background: Woman aged 42, AMH 1.2 ng/mL, history of 3 spontaneous miscarriages (all at 8-10 weeks gestation), both partners have normal karyotypes.
Decision Analysis: The core issue in this case is the significantly increased rate of embryonic aneuploidy with age. PGT-A in Thailand can screen out embryos with abnormal chromosome numbers before transfer, increasing the clinical pregnancy rate per transfer from 30%-35% to 50%-60% (data from clinical statistics of multiple Thai centers, 2022-2023). However, note that low AMH may lead to fewer eggs retrieved and potentially limit the number of blastocysts available for biopsy. It is recommended to assess ovarian response beforehand before making a decision.
Scenario 2: Monogenic Disease Carrier
Background: Both partners are carriers of β-thalassemia. They previously had a child with severe thalassemia and wish to have a healthy child this time.
Decision Analysis: This case requires PGT-M testing. Some centers in Thailand collaborate with NGS laboratories to design testing protocols for specific mutation sites in the HBB gene. The patient needs to complete a confirmed thalassemia gene diagnosis report for the proband and both partners domestically and send blood samples to the Thai laboratory for pre-testing. The probe design cycle is about 4-6 weeks. After successful completion, the cycle can proceed. Prenatal diagnosis is required after transfer to confirm the test results.
Scenario 3: Carrier of Balanced Chromosomal Translocation
Background: The male partner is a carrier of a balanced chromosomal translocation [46,XY,t(2;5)(q21;q31)], the female partner has a normal karyotype. They have been trying to conceive for 2 years without success and have no history of miscarriage.
Decision Analysis: Carriers of balanced translocations can produce a large number of unbalanced gametes during sperm formation, leading to embryonic chromosomal segment duplications or deletions. PGT-SR in Thailand can use SNP haplotype analysis or NGS combined with parental verification to select embryos with normal chromosomal structure. The testing complexity is higher than PGT-A; pre-testing requires simultaneous analysis of the male's translocation breakpoints and family haplotypes, with a cycle of about 4-5 months.
Module Q: Frequently Asked Questions6. Frequently Asked Questions
- Can PGT in Thailand detect all genetic diseases? No. PGT-M can only detect monogenic diseases with known pathogenic gene loci. It cannot detect unknown genes or polygenic complex diseases (e.g., congenital heart disease, diabetes). The testing scope depends on the gene panels developed by the laboratory and the completeness of family verification.
- Can miscarriage still occur after transferring a PGT-A normal embryo? Yes. PGT-A only screens for chromosomal number abnormalities; it cannot rule out embryonic mosaicism, small segment deletions/duplications (<5Mb), or miscarriages caused by maternal factors. The miscarriage rate for PGT-A normal embryos is about 5%-10%, lower than the 15%-20% for unscreened embryos.
- How are mosaic embryos handled in Thai PGT? NGS can detect embryos with 20%-80% mosaicism. Thai centers typically classify mosaic embryos into low proportion (20%-40%) and high proportion (40%-80%). Low-proportion mosaic embryos may be considered for transfer after full disclosure of risks, while high-proportion mosaic embryos are usually recommended for discard.
- What tests need to be done domestically before undergoing PGT in Thailand? The following must be completed: Karyotype analysis of both partners, genetic disease gene test report (if applicable), sex hormone panel + AMH, semen analysis, infectious disease screening (HIV, Hepatitis B, Hepatitis C, Syphilis, Cytomegalovirus, etc.). PGT-M/PGT-SR also requires blood samples from family members for pre-testing.
- What is the accuracy rate of PGT in Thailand? The chromosome detection accuracy for PGT-A is >98% (false positive rate <2%, false negative rate <0.5%). The single gene locus accuracy for PGT-M is about 96%-98%. Due to potential allele dropout (ADO) or chromosomal recombination interference, final confirmation requires prenatal diagnosis.
⚠ Risk Reminder
- Testing Limitations: PGT is an embryo screening technology and cannot replace prenatal diagnosis. All pregnancies resulting from PGT-screened embryos should undergo amniocentesis or chorionic villus sampling for prenatal genetic confirmation at 16-20 weeks of gestation.
- Risk of Embryo Biopsy Damage: The potential impact of trophectoderm cell biopsy on the embryo is still under research. Current data shows a post-biopsy blastocyst survival rate >95%, but long-term follow-up data are still needed.
- Differences in Laboratory Standards: PGT technology platforms and personnel experience vary among Thai centers. It is recommended to choose a center with JCI certification, an independent genetics laboratory, or long-term collaboration with a reputable third-party genetic institution.
- Policy and Ethical Risks: Thai laws regarding PGT indications, sex selection, and embryo disposition may change. It is advisable to confirm the latest medical regulatory policies before starting the cycle.
- Completeness of Genetic Counseling: PGT-M and PGT-SR are highly dependent on the completeness of family verification. If the proband's sample cannot be obtained or the family pedigree is incomplete, it may lead to probe design failure or unclear test results. Patients must be fully informed of such situations during counseling.
