Introduction and Background
In modern IVF practice, the transfer of a single high-quality embryo through elective single embryo transfer (eSET) has become increasingly common as the primary approach to prevent multiple pregnancies. Advances in embryo selection and cryopreservation have since enabled eSET to emerge as a safer, viable alternative.1 This shift in practice addresses one of the most critical complications associated with IVF—multiple pregnancies—which has been well-documented as adding significant complexity and risk to pregnancies.2
The historical context for this change is important to understand. Initially, multiple embryo transfers were common in IVF due to low implantation rates, as practitioners attempted to increase the likelihood of successful pregnancy. However, this approach led to increased risks of multiple pregnancies, which can cause serious maternal complications including preeclampsia and hypertension, as well as fetal risks such as preterm birth, low birth weight, and cerebral palsy.3,4
Research has demonstrated that when high-quality embryos are available, eSET can maintain success rates while eliminating the risk of multiple pregnancies.2 However, the implementation of eSET requires careful patient selection, as individual variability in fertility factors remains a significant consideration in determining the most appropriate treatment approach.3
Clinical Outcome Success Rates
Research has shown that while eSET may result in lower immediate pregnancy rates compared to double embryo transfer in fresh IVF cycles, this difference can be effectively overcome through subsequent frozen embryo transfers.5,6 The ‘one plus one’ strategy—eSET followed by a frozen embryo transfer— optimizes outcomes has proven to be more effective than transferring multiple embryos simultaneously, as it leads to increased implantation chances while avoiding multiple gestations.
Real-world implementation data supports the effectiveness of eSET programs. In Switzerland, a universal eSET approach achieved cumulative pregnancy rates of 48.9% and live birth rates of 33.4% per oocyte collection, while completely eliminating multiple pregnancies.7 Similarly, Belgium saw a dramatic reduction in multiple pregnancy rates from 25% to 11.9% following the implementation of mandatory SET for patients under 36 years.8
The success of eSET has been demonstrated across different age groups. Studies have shown that eSET can be effectively applied to women aged 36-39 years, maintaining comparable cumulative pregnancy and live birth rates while significantly reducing multiple birth risks.9,10 When combined with frozen embryo transfers, Devroey et al.11 reported no significant difference in cumulative live birth rates (42.9% vs. 38.8%, p > 0.05).11
However, it’s important to note that while eSET significantly reduces multiple pregnancy risks, it may decrease the chance of live birth in a fresh IVF cycle.8,12 This initial difference is typically overcome through subsequent frozen embryo transfers, leading to comparable cumulative success rates while maintaining the safety benefits of single embryo transfer.9
Benefits and Evidence Supporting eSET
The primary benefit of eSET lies in its proven ability to significantly reduce multiple pregnancy rates without compromising overall success rates. Studies have demonstrated that implementing eSET can reduce multiple pregnancy rates from 25% to as low as 5%.13 This reduction is particularly significant given that twin gestations are associated with a 5-10 fold increase in fetal and maternal complications.14
Modern embryo selection techniques have enhanced the effectiveness of eSET. The use of comprehensive chromosome analysis for embryo selection has optimized eSET outcomes by identifying embryos with the highest developmental potential.14 This advancement has made it possible to achieve acceptable pregnancy rates while minimizing the risk of multiple pregnancies.15
Cost-effectiveness analyses have shown that eSET can be economically advantageous. Despite potentially requiring more cycles to achieve pregnancy, the overall costs associated with eSET are comparable to or lower than multiple embryo transfer approaches due to reduced complications and neonatal care expenses. Gerris et al.16 found eSET reduced neonatal costs by €5,000 per case. Studies have demonstrated that while maternal costs remain similar, the neonatal care costs are significantly lower with eSET compared to double embryo transfer.17
The benefits of eSET extend across different patient populations. While initially recommended primarily for younger patients with good prognosis, research now supports extending eSET to women of advanced maternal age, as it can maintain treatment efficacy while improving safety outcomes.18 This approach has become particularly meaningful for older women undergoing assisted reproductive technology, given their increased risk of obstetrical complications.19
Leading professional organizations now recognize that successful IVF treatment should be measured by singleton birth rates rather than just pregnancy rates, acknowledging that a single healthy baby represents the optimal outcome.20 This shift in perspective has helped establish eSET as the most efficient approach to achieve better perinatal and neonatal outcomes.21
Challenges and Considerations
The successful implementation of eSET programs faces several significant challenges that must be carefully considered. A primary challenge is the need for advanced embryo selection capabilities, as the success of eSET heavily depends on the ability to identify embryos with the highest implantation potential.22 This becomes particularly crucial for older patients, where aneuploidy presents a major hurdle to success.23
The quality of available embryos significantly impacts treatment decisions. Sadeghi24 suggests poor-quality embryos may release factors inhibiting high-quality embryo implantation. This understanding has led to recommendations focusing on transferring only top-quality embryos, even if this means transferring fewer embryos overall.
Access to treatment represents another significant challenge, particularly in regions where IVF services are not covered by public healthcare systems or private insurance.25 The financial burden of multiple IVF cycles can influence both provider and patient decision-making regarding embryo transfer strategies.
A crucial consideration in eSET implementation is the balance between medical recommendations and patient autonomy. While eSET may be clinically preferable, factors such as advanced maternal age, prolonged infertility, and patient preferences must be carefully weighed in the decision-making process.26 Patients may prioritize immediate success over safety, necessitating tailored counseling. The success of eSET programs ultimately depends on effective patient education about both benefits and limitations, combined with a comprehensive approach that includes successful cryopreservation programs and access to subsequent frozen embryo transfers.22
Implementation and Regulation Worldwide
Implementation of eSET varies considerably worldwide, with adoption being most successful in countries that combine regulatory oversight with financial support for fertility treatments.27 The combination of insurance coverage and restrictions on embryo numbers has proven particularly effective in encouraging eSET adoption.27,28
Regional differences in eSET adoption are striking. While Europe achieved 38% eSET rates in 2016 across 1,200 clinics,28 the United States reaches 71%, Southeast Asia reports only about 10.2% of cycles using single embryo transfer.29 Countries with state-funded fertility treatment and strong regulatory frameworks, such as Australia, have achieved particularly high eSET rates of over 75%, resulting in multiple pregnancy rates below 6%.
Japan provides a notable example of successful regulatory implementation. Following the introduction of specific guidelines by medical societies in 2007-2008, Japan saw significant improvements in outcomes, including a dramatic reduction in twin pregnancies from 33.9% to 13% and decreased rates of preterm delivery and low birth weight.30
The primary barriers to widespread eSET implementation include treatment costs, lack of legislative policies in some regions, and inconsistent availability of ART services.29 Patient education has emerged as an important tool in implementation strategies, with studies showing that focused education about maternal and perinatal risks can effectively reduce patient preference for multiple embryo transfers.27
The Integration of AI in Embryo Selection
The integration of AI in embryo selection offers significant advantages, addressing longstanding challenges in IVF practice. Traditional embryo assessment methods have been subjective, time-consuming, and prone to variability.31 AI systems provide standardized, objective evaluations, outperforming trained embryologists by up to 24.7% in identifying implantation-capable embryos.32
Key Benefits of AI in Embryo Selection
Reduced Observer Variability: AI-based systems eliminate inter- and intra-observer variability in embryo assessment.33 This consistency is essential as the demand for ART treatments continues to grow, increasing manual workload.34
Efficiency in Data Processing: AI tools efficiently process large datasets while maintaining consistent quality standards. They expedite calculations and improve precision, reducing the manual workload for embryologists.35
Improved Patient Experience: By optimizing treatment plans, AI systems help reduce the financial, physical, and emotional burden on patients, minimizing the need for repeated IVF cycles.36
Enhanced Clinical Insights: Deep learning techniques support more objective and accurate results, offering a noninvasive, efficient approach to embryo selection.37,38
Limitations and Challenges
Despite the advancements in AI-driven embryo selection, the ultimate decision-making authority remains with clinicians. The effectiveness of these systems depends significantly on how closely clinicians adhere to AI-generated recommendations.37
AI Tools and Technologies in Embryo Selection. Machine Learning-Based Image Analysis (Table 1)
Time-Lapse Integration Systems
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AI systems combine continuous observation with analysis to track developmental timing and morphokinetic parameters.40
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Compatible with existing IVF laboratory protocols.45
Clinical Implications
Clinical studies indicate that combining AI with time-lapse imaging improves embryo selection outcomes. AI-based selection systems have achieved up to 75% accuracy in predicting pregnancy success, compared to 65% accuracy by embryologists.46 AI tools like iDAScore have reduced evaluation time while maintaining consistent performance.43 See Appendix 1 for standardized eSET protocols.
Future Directions and Challenges
The future of AI in embryo selection lies in the development of multi-modal models integrating morphological, genetic, and metabolic data. Machine learning algorithms may soon assist with optimizing endometrial receptivity and predicting IVF success based on lifestyle factors.47 Challenges include integrating diverse datasets while addressing ethical concerns like AI bias and patient data security
Conclusion
While eSET should not be universally mandated due to patient variability, it should be the default for good-prognosis cases. The adoption of eSET has demonstrated significant benefits in improving IVF safety, reducing complications from multiple pregnancies while maintaining comparable success rates. The integration of advanced embryo selection techniques, supported by AI technologies, continues to enhance outcomes. Regulatory frameworks and patient education are essential to successful implementation worldwide, with future innovations likely to further optimize embryo selection and improve fertility treatment success rates.
Funding Statement
There has been no funding received for this study.
Competing Interest
None
Submission declaration & Declaration of interest
The manuscript has never been published before. There are no other publications considering it. The author declares no conflict of interest and have no relevant affiliations or financial involvement with any organization or entity with a financial interest. This includes employment, consultancies, honoraria, expert testimony, grants or royalties.