How is Oocyte Activation (OA) Technology in Thailand: Principles, Suitable Candidates, and Clinical Analysis

AI Summary

1. Starting from a Real Outpatient Consultation

A 36-year-old woman, with an AMH of 1.8, completed one ICSI cycle at another hospital due to severe male oligoasthenospermia. Of 11 mature eggs, only 1 showed signs of fertilization, and the rest all failed. The couple came to the clinic with a thick stack of medical records and asked, "Doctor, can the OA technology they talk about in Thailand really help solve our fertilization problem? Am I suitable for this?"

This question is not an isolated case. In reproductive clinics, although the incidence of fertilization failure or low fertilization rate after ICSI is not high (about 1%–5%), it is a devastating blow for couples who experience it. "Oocyte Activation" (OA) technology is an important technical option specifically for this problem. As one of the destinations for assisted reproduction in Asia, some centers in Thailand are indeed equipped with this technology, but patients often have blind spots in their understanding of its true principles, indications, and limitations.

This article systematically breaks down what OA technology is, why it works, who is suitable, who is not, and the actual situation of its implementation in Thailand from a clinical reproductive medicine perspective, helping patients build a clear and rational cognitive framework.

2. What is OA Technology? — Direct Answer to the Question

Oocyte Activation (OA) technology refers to the process of artificially inducing regular fluctuations in calcium ion concentration within the egg (simulating the "calcium oscillations" during natural fertilization) based on ICSI (Intracytoplasmic Sperm Injection). This initiates egg activation, completes the second meiotic division, extrudes the second polar body, and ultimately forms a normal fertilized egg.

In natural fertilization, after the sperm enters the egg, it releases a factor called "phospholipase C zeta" (PLCζ), which triggers the repeated release of calcium ions within the egg. This is the biological switch for egg activation. When sperm have functional defects (such as globozoospermia, acephalic spermatozoa, extremely poor sperm motility) or cryodamage, they cannot provide sufficient PLCζ, leading to failure of egg activation and fertilization failure after ICSI.

OA technology "replaces" the sperm in completing this activation step through exogenous means. The main methods include:

• Calcium ionophores (e.g., ionomycin, A23187): Directly promote calcium release within the egg. They are the most widely used in clinical practice and have the most research data.
• Electrical activation: Uses a brief electrical pulse to change the egg's membrane potential, inducing calcium influx. Some centers use this method.
• Other auxiliary activation methods: Such as using strontium chloride, puromycin, etc., but these are less common clinically.

Currently, centers in Thailand that perform OA technology mostly use calcium ionophore protocols. The procedure is integrated with conventional ICSI and is carried out in the embryology laboratory.

3. Why Does Fertilization Failure Occur After ICSI?

To understand the value of OA technology, one must first understand the causes of fertilization failure. Clinically, fertilization failure or low fertilization rate (<30%) after ICSI mainly stems from three categories of factors:

OA technology is primarily aimed at fertilization failure caused by sperm factors. It has limited effectiveness for egg factors, and for technical factors, the solution lies in optimizing the procedure, not relying on OA.

4. How Do Doctors View OA Technology? — Clinical Value Coupled with Caution

In the field of reproductive medicine, OA technology is considered the "first-line rescue option" for fertilization failure after ICSI, especially for couples with a clear diagnosis of sperm activation deficiency. Clinical research data shows:

• For patients with complete fertilization failure in previous ICSI cycles, using OA can increase the fertilization rate from nearly 0% to 60%–80%, with no significant difference in high-quality embryo rates compared to conventional ICSI.
• For patients with globozoospermia (100% round-headed sperm), OA is almost the only way to achieve fertilization, with clinical pregnancy rates reaching 30%–50% (depending on female age and egg quality).
• In cycles using frozen sperm (especially from patients with severe oligoasthenospermia), OA can increase the fertilization rate by 15%–30%.

However, doctors also remain cautious for three reasons:

1. Insufficient long-term safety data: OA technology originated in the 1990s. Although thousands of children have been born, large-scale, multi-center long-term follow-up studies are still limited. Theoretical epigenetic risks (such as imprinting gene abnormalities) have not been completely ruled out.
2. Not all fertilization failures are suitable for OA: If the failure is due to abnormalities in the egg's own activation pathway or immature ooplasm, OA may be ineffective or even increase the rate of abnormal fertilization.
3. Technical differences between centers: The specific protocols for OA (type of activator, concentration, treatment time) are not yet fully standardized. The experience and quality control level of different laboratories directly affect the outcome.

5. The Most Easily Overlooked Details

Patients and some practitioners often overlook the following key points when considering OA technology:

• Sperm activation capacity testing: Before deciding to use OA, if conditions permit, testing for sperm phospholipase C zeta activity or a mouse oocyte activation test (MOAT) should be performed to determine if there is a sperm activation defect. Some centers in Thailand offer such tests, but they are not standard.
• Assessment of egg maturity: OA technology requires a relatively high level of egg maturity. Only MII stage eggs (those that have extruded the first polar body) can be activated. If the egg itself is immature or post-mature, the effect of OA will be diminished.
• Risk of abnormal fertilization: OA can lead to polyspermy (although ICSI itself is a single sperm injection, abnormal activation can cause abnormal egg division) or triploid embryos, with an incidence of about 3%–8%, requiring strict monitoring by the embryology laboratory.
• Cycle cancellation rate: Even with OA, about 10%–20% of cycles are still cancelled due to fertilization failure or lack of usable embryos. Patients need to have realistic expectations.

6. The Most Common Pitfalls

Based on a review of numerous consultation cases, the following "pitfalls" are the most common:

• Equating OA with "improving egg quality": OA solves the activation problem, not egg quality. If the egg itself has chromosomal abnormalities or poor mitochondrial function, OA cannot improve embryo developmental potential.
• Believing that earlier use of OA is always better: For patients without clear indications, OA is not only unhelpful but may introduce unnecessary risks. Routine use of OA in the first ICSI cycle is not recommended unless there are clear high-risk factors (such as globozoospermia).
• Overly trusting that "Thai technology is more advanced": OA technology is performed worldwide. While some centers in Thailand have experience, not all Thai reproductive centers have the same level of laboratory quality control. When choosing, one should examine the center's specific equipment and case data, not just rely on the "Thailand" label.
• Ignoring genetic counseling: Some sperm activation disorders are related to genetic factors (such as PLCZ1 gene mutations). If a genetic defect is confirmed, the risk of inheritance for offspring must be considered, and PGT may be necessary.

7. Actual Procedure: How is OA Technology Implemented in Thailand?

Using a reproductive center in Thailand with OA technology capabilities as an example, the standard procedure is as follows:

What needs to be prepared? In addition to the routine documents and medical reports required for IVF, detailed records of previous ICSI cycles (including fertilization rates, embryo photos, etc.) are needed for the doctor to determine the necessity of OA. Some centers require the male partner to undergo additional sperm activation function testing.

How long does it take? OA itself only adds about 15–30 minutes of laboratory processing after the ICSI procedure and does not extend the overall cycle length. However, pre-treatment evaluation and genetic counseling may require an additional 1–2 weeks.

8. Suitable and Unsuitable Candidates

✅ Suitable Candidates

• Patients with complete fertilization failure or a fertilization rate ≤30% in a previous ICSI cycle, where a sperm activation defect is suspected after excluding egg factors.
• Patients with globozoospermia, especially those with 100% round-headed sperm.
• Patients with acephalic spermatozoa or extremely poor motility due to sperm tail defects.
• Patients using frozen sperm (especially when pre-freeze sperm quality was very poor) with a history of low ICSI fertilization rates.
• Patients with a genetic diagnosis of PLCZ1 gene mutation or other gene variants related to sperm activation.

❌ Unsuitable Candidates

• Patients where ICSI fertilization failure is clearly caused by egg factors (e.g., egg maturation arrest, immature ooplasm, abnormal activation pathways in aged eggs).
• First ICSI cycle with no clear high-risk factors for fertilization failure; routine use of OA is not recommended.
• Patients with a very low number of eggs (e.g., ≤3 eggs retrieved), as OA may increase the risk of abnormal fertilization with unclear benefits.
• Patients or couples who are not willing to accept the uncertainties of the technology (e.g., limited long-term safety data).

9. Frequently Asked Questions (QA)

Q1: How successful is OA technology in Thailand?
The "success rate" of OA technology needs to be broken down: In terms of fertilization rate, clinical studies report an increase from less than 30% to 60%–80%. In terms of clinical pregnancy rate, it depends on the woman's age, egg quality, and embryo development. Currently, the live birth rate reported in the literature is about 25%–45%, which is slightly lower or comparable to conventional ICSI in populations without fertilization failure. Note that no center can guarantee a specific success rate.

Q2: Can OA technology cause health problems for the baby?
Current follow-up data (largest sample about 1500 offspring, followed up to school age) show no significant differences in birth defect rates, intellectual development, and physical development between OA offspring and conventional ICSI offspring. However, the sample size is still insufficient to rule out rare risks (such as imprinting disorders). It is recommended to choose a center with an offspring follow-up plan and inform the pediatrician about the relevant technical background after birth.

Q3: Which centers in Thailand can perform OA? How to judge if they are reliable?
Some large reproductive centers in Bangkok, Thailand (such as Jetanin, BNH, Phyathai, etc.) and their affiliated laboratories have experience with OA technology. Criteria for judgment: ① The center can provide data on the number of OA cycles and fertilization rates from the past 1–2 years; ② Whether the embryology laboratory has an independent quality control system; ③ Whether the doctor recommends OA based on sperm activation test results rather than just "experience."

Q4: Are OA and AOA the same thing?
Clinically, OA (Oocyte Activation) and AOA (Artificial Oocyte Activation) are often used interchangeably, both referring to artificial oocyte activation. Some literature specifically refers to AOA as the method using calcium ionophores, while OA is a broader term. When consulting, just confirm the specific protocol used by the center.

10. Practitioner's Observation: The Real Situation of OA Technology in Thailand

As a doctor with over ten years of clinical experience in assisted reproduction, I have observed several characteristics of OA technology application in Thailand:

• Early introduction but low prevalence: Some centers in Thailand started applying OA technology around 2010, but due to strict indications and high laboratory requirements, currently no more than 10 centers routinely perform it.
• Polarized patient awareness: Some patients are completely unaware of OA, while others see it as a "universal rescue technique." Both extremes need correction.
• Significant cost variation: The additional charge for OA in Thailand ranges from 20,000 to 50,000 Thai Baht (approximately 4,000–10,000 RMB). The difference mainly comes from the brand of activator and laboratory labor hours. It is advisable to ask for a detailed breakdown to understand what specific services are included in the cost.
• Lack of uniform standards: The concentration of calcium ionophore, treatment time, and number of washes vary between centers. This is one of the biggest limitations of the technology currently. Choosing a laboratory with extensive experience is more important than choosing the "latest technology."