Clinical Application and Laboratory Quality Control Analysis of Vitrification in Thailand

Author identity tag (Reproductive Specialist)

In last week's outpatient clinic, a 34-year-old patient with poor ovarian response came for consultation with a brochure from a Thai institution. She wanted to know how reliable vitrification technology really is, especially whether the post-thaw survival rate of eggs is truly "close to 100%" as advertised. She was concerned about irreversible cell damage caused by freezing and whether technical differences between laboratories would affect the final outcome. Such questions are not uncommon in reproductive clinics, reflecting patients' need to understand the true level of freezing technology.

1. Direct Answer: What is the Level of Vitrification Technology in Thailand

Vitrification is currently the standard freezing protocol adopted by most assisted reproduction laboratories in Thailand. Compared with traditional slow freezing, vitrification uses an ultra-high cooling rate (approximately -20,000°C/min) to instantly transform the liquid inside and outside the cell into a glassy state, preventing ice crystal formation. Under conditions of standardized operation and adequate equipment, oocyte survival rates in mainstream Thai laboratories range from 90% to 95%, and embryo survival rates exceed 95%, with some centers reporting data as high as 97%–98%. However, it is important to note that survival rate does not equal live birth rate; final pregnancy outcomes also depend on factors such as embryo quality, endometrial receptivity, and maternal age.

2. Why Patients Are Generally Concerned About Freezing Technology Quality

Patient concerns about freezing technology mainly focus on three aspects:

• Risk of cell damage: Ice crystal formation during freezing may disrupt cell membrane and organelle structures.
• Developmental potential after thawing: Whether frozen embryos or eggs can continue to divide and implant normally after thawing.
• Inter-laboratory variability: Differences in equipment, reagents, and operational experience between institutions can lead to outcome fluctuations.

These concerns are reasonable. Although vitrification is a mature technology, its actual effectiveness is highly dependent on operational details and quality control systems. As Thailand is a popular destination for cross-border assisted reproduction, laboratory standards vary widely, making an objective understanding of the current technical status essential.

3. Reproductive Specialist Perspective: How to Evaluate the Clinical Value of Vitrification

In clinical decision-making, we do not judge a laboratory's level solely based on whether it uses vitrification. Instead, we focus on the following aspects:

• Does the laboratory have stable quality control records?
• Have the embryologists undergone systematic training and accumulated sufficient case experience?
• Is the preparation and batch management of cryoprotectants standardized?
• Are there regular thawing tests (e.g., sample thawing verification of donor eggs)?

4. Objective Differences in Technical Levels Between Countries

The basic principles of vitrification technology are identical in countries such as Thailand, the United States, Japan, and China. Differences mainly lie in laboratory management, personnel training, and quality control standards.

From the data, the survival rates of top-tier Thai institutions are close to high international standards. However, actual data from small and medium-sized institutions may fluctuate, and some institutions' publicly reported data lack third-party verification.

5. Most Easily Overlooked Laboratory Details

5.1 Equilibration Time of Cryoprotectants

Too long or too short an equilibration time can affect cell survival. Standard protocols typically require gradient equilibration at room temperature, with precise timing for each step. In practice, the operator's experience directly influences this stage.

5.2 Purity and Temperature Stability of Liquid Nitrogen

Temperature fluctuations in liquid nitrogen storage tanks, the frequency of liquid nitrogen replacement, and potential microbial contamination are easily overlooked variables. Some laboratories perform regular filtration and microbial testing of liquid nitrogen.

5.3 Consistency of Thawing Operations

The thawing process is highly sensitive to temperature gradients and dilution rates. Whether the operator follows the standard protocol for stepwise dilution, uses a pre-warmed plate, and allows sufficient recovery time for cells after thawing all affect the final outcome.

6. Common Pitfalls When Choosing an Institution

• Focusing only on advertised data, not sample size. A 95% survival rate could be based on 20 samples or 2000 samples, with vastly different reliability.
• Ignoring laboratory accreditation. Whether the lab has passed ISO 15189, JCI, or regular audits by local health authorities is a hard indicator of standardized operation.
• Not knowing operator qualifications. The experience of different embryologists at the same institution can vary by 5–10 years; it is advisable to ask who will perform the procedure.
• Confusing survival rates of "frozen embryos" and "frozen eggs." Egg freezing is technically more challenging than embryo freezing, with survival rates typically 2–5 percentage points lower; advertising often blurs this distinction.

7. Standard Vitrification Procedure

The following is a general procedure used in mainstream Thai laboratories, with minor variations between institutions:

1. Assessment and Informed Consent: Confirm indications, rule out contraindications, and sign the freezing informed consent form.
2. Preparation of Cryoprotectants: Prepare equilibration and vitrification solutions containing ethylene glycol, DMSO, and sucrose.
3. Equilibration Treatment: Place eggs or embryos sequentially into equilibration and vitrification solutions, timing precisely at room temperature.
4. Loading and Plunging into Liquid Nitrogen: Load the sample onto a freezing carrier (e.g., Cryotop) and quickly immerse it in liquid nitrogen (entire process within 30 seconds).
5. Storage: Transfer the carrier to a liquid nitrogen storage tank, record the location, and update the information system.
6. Thawing: Remove the carrier from liquid nitrogen, immediately immerse it in pre-warmed thawing solution at 37°C, and dilute the cryoprotectant in a stepwise manner.
7. Survival Assessment: Evaluate cell morphology and survival status under a microscope; surviving cells proceed to further culture or transfer.

The entire process requires strict time control; any delay in any step can lead to a decrease in survival rate.

8. Cost Breakdown and Influencing Factors

Cost differences mainly stem from institutional positioning, equipment investment, and whether subsequent transfer cycles are included. Some institutions' quotes do not include thawing operation fees or long-term storage fees, so these should be confirmed in advance.

9. Answers to Frequently Asked Questions

9.1 Does vitrification affect the chromosomal structure of embryos?

Current evidence indicates that vitrification itself does not increase the rate of chromosomal aneuploidy. The chromosomal status of an embryo is primarily determined by egg and sperm quality, not the freezing process. However, freezing operations may cause further damage to embryos with pre-existing chromosomal abnormalities, so PGT testing should be completed before freezing.

9.2 Is the success rate of frozen embryo transfer lower than that of fresh embryo transfer?

For individuals with poor endometrial conditions or at risk of ovarian hyperstimulation, the clinical pregnancy rate of frozen embryo transfer is not inferior to that of fresh embryo transfer, and may even be superior in certain subgroups. The key factor is the synchronization between endometrial receptivity and the embryo, not the freezing technology itself.

9.3 How long can eggs be stored after freezing?

Theoretically, storage in liquid nitrogen (-196°C) can completely halt cellular metabolism, and no significant decline in survival rate has been observed for storage periods exceeding 10 years. However, in practice, this is limited by institutional storage policies and the patient's own plans; it is recommended to use them within 5 years.

9.4 Who is suitable for egg vitrification?

• Unmarried women who need radiotherapy or chemotherapy for tumors
• Women under 38 years old delaying childbearing for social reasons
• Women with diminished ovarian reserve who are not yet ready to conceive
• Simultaneous freezing and storage when receiving donor eggs

9.5 In which situations is vitrification not suitable?

• Very poor egg or embryo quality (e.g., severe fragmentation, abnormal morphology)
• Uncontrolled reproductive tract infections
• Patient allergy to components of the cryoprotectant (rare)

10. Practitioner's Observation: How to Judge a Laboratory's Freezing Level

In Thailand, the level of laboratory investment varies significantly between institutions. Some chain group centers have dedicated quality control teams and backup liquid nitrogen systems, while smaller clinics may lack redundant backups. It is advisable to view the laboratory environment via video or an on-site visit before making a decision.

11. When is it Suitable to Choose Vitrification for Preservation

• Planning to undergo PGT testing and needing to wait for genetic results before transfer
• High number of eggs retrieved during the stimulation cycle, requiring freezing of surplus embryos
• Need to delay transfer due to endometrial thickness, hormone levels, or risk of ovarian hyperstimulation
• Women requiring ovarian-damaging treatment (e.g., chemotherapy) who wish to preserve fertility

12. When is it Not Suitable to Rely on Vitrification

• The laboratory's quality control system is unclear and cannot provide traceable records
• The institution advertises survival rates far above the industry-recognized range (e.g., claiming egg survival rates >98%) without specifying sample size
• Operator experience is insufficient or turnover is too high