Assess your fertility preservation options with personalized estimates for egg freezing success and costs
Medical Disclaimer: This calculator provides estimates only. Consult with a fertility specialist for personalized medical advice.
Your Information
Anti-Müllerian Hormone indicates ovarian reserve
Your Egg Freezing Assessment
Enter your information and click “Calculate Egg Freezing Plan” to see results
Live Birth Probability
Based on your profile
Eggs Needed for Desired Family
Cost Estimate
Estimated Timeline
Success Probability by Age
Recommended Next Steps
About Egg Freezing
The Egg Freezing Process
- Ovarian Stimulation: Daily hormone injections for 10-14 days to stimulate egg development
- Monitoring: Regular ultrasound and blood tests to track follicle growth
- Trigger Shot: Final medication to prepare eggs for retrieval
- Egg Retrieval: Minor surgical procedure under sedation to collect eggs
- Vitrification: Rapid freezing process to preserve egg quality
Key Factors in Success
- Age at Freezing: Younger eggs have higher success rates
- Ovarian Reserve: AMH and AFC indicate how many eggs you have
- Egg Quantity: More eggs frozen increases future options
- Clinic Expertise: Experience and success rates matter
- Lifestyle Factors: Overall health impacts egg quality
Frequently Asked Questions
What is the ideal age for egg freezing?
The optimal time is typically in your late 20s to mid-30s when egg quantity and quality are still high. Success rates decline significantly after age 35.
How long can eggs be stored?
Frozen eggs can be stored for many years without significant deterioration. Current evidence suggests they remain viable for at least 10+ years.
What are the costs involved?
Costs typically include consultations, medications, monitoring, the retrieval procedure, and annual storage fees. Prices vary by clinic and location.
Does insurance cover egg freezing?
Coverage varies widely. Some plans cover diagnostic testing, while few cover the full procedure unless medically necessary. Check with your provider.
Understanding the Brigham Egg Freezing Calculator: A Comprehensive Guide
Egg freezing has emerged as one of the most significant advancements in reproductive medicine, offering individuals the opportunity to preserve fertility potential against the natural decline associated with aging. The Brigham Egg Freezing Calculator represents a sophisticated analytical tool developed by leading reproductive specialists to help individuals make informed decisions about fertility preservation. This powerful calculator combines clinical data, statistical modeling, and personalized factors to provide accurate predictions about egg freezing outcomes and future family planning possibilities.
The Brigham calculator stands at the intersection of reproductive science and data analytics, transforming complex biological processes and statistical probabilities into accessible, personalized insights. By modeling the relationship between age, ovarian reserve, treatment protocols, and cryopreservation outcomes, this tool enables individuals to approach fertility preservation with greater clarity and confidence, supported by evidence-based predictions.
This comprehensive guide explores the Brigham Egg Freezing Calculator in exhaustive detail, examining its methodology, clinical foundations, practical applications, and the sophisticated algorithms that power its predictions. Whether you’re considering egg freezing for medical reasons, career planning, or personal circumstances, this article will provide the knowledge needed to understand and leverage this powerful reproductive planning tool effectively.
The Science of Ovarian Aging and Fertility Preservation
Understanding the biological foundations of ovarian aging is essential for appreciating the predictive capabilities of the Brigham Egg Freezing Calculator. The tool’s accuracy stems from its incorporation of established reproductive science principles and clinical data.
Ovarian Reserve and Follicle Dynamics
The calculator models the fundamental relationship between chronological age and ovarian reserve:
- Primordial Follicle Pool: Women are born with approximately 1-2 million follicles, which declines throughout life
- Accelerated Depletion: Follicle loss accelerates after age 35, with significant qualitative decline
- AMH Correlation: Anti-Müllerian Hormone levels strongly correlate with remaining follicle count
- Individual Variation: Significant differences in ovarian aging patterns between individuals
Egg Quality and Aneuploidy Rates
The calculator incorporates age-related changes in egg quality:
Egg Quality Decline
By age 40, approximately 50-60% of eggs are chromosomally abnormal (aneuploid), compared to 20-25% at age 30, significantly impacting live birth rates from frozen eggs.
- Mitochondrial function decline with advancing age
- Cumulative DNA damage in oocytes over time
- Spindle apparatus abnormalities affecting chromosome segregation
- Cellular environment changes impacting egg development
Cryopreservation Science and Success Rates
The calculator models vitrification outcomes and thaw survival rates:
- Vitrification technique survival rates (typically 90-95%)
- Fertilization rates with ICSI (70-80% for thawed eggs)
- Blastocyst development rates from fertilized eggs
- Live birth rates per euploid embryo transferred
These biological principles form the foundation upon which the Brigham calculator builds its predictive models, translating complex reproductive science into actionable insights for individuals considering fertility preservation.
Key Input Parameters and Clinical Factors
The accuracy of Brigham Egg Freezing Calculator predictions depends on understanding and properly configuring key clinical and personal parameters. Each variable significantly impacts the resulting probability estimates and recommendations.
Demographic and Baseline Characteristics
Fundamental personal factors that influence egg freezing outcomes:
| Parameter | Impact Range | Measurement Method | Clinical Significance |
|---|---|---|---|
| Current Age | High Impact | Chronological age | Primary determinant of egg quantity and quality |
| AMH Level | High Impact | Blood test (ng/mL) | Strong predictor of ovarian response to stimulation |
| AFC Count | High Impact | Transvaginal ultrasound | Direct assessment of antral follicle population |
| FSH Level | Moderate Impact | Blood test (mIU/mL) | Indicator of ovarian reserve and pituitary feedback |
| BMI | Moderate Impact | Body Mass Index | Affects medication dosing and response |
| Reproductive History | Variable Impact | Medical history | Previous pregnancies may indicate better prognosis |
Treatment Protocol Variables
The calculator models how different stimulation approaches affect outcomes:
Expected Mature Eggs = Baseline Ovarian Reserve × Stimulation Response Factor × Protocol Efficiency
This calculation estimates the number of metaphase II eggs likely to be retrieved based on individual characteristics and treatment approach.
The algorithm incorporates data from thousands of cycles to predict individual response patterns.
Laboratory and Cryopreservation Factors
The calculator includes laboratory-specific success rates:
- Clinic-specific vitrification and thaw survival rates
- Fertilization efficiency with ICSI techniques
- Blastocyst development and euploidy rates
- Cumulative success rates across multiple cycles
Future Usage Scenarios
The calculator models different future family planning scenarios:
- Age at planned embryo creation and transfer
- Number of desired children
- Partner sperm versus donor sperm considerations
- Preimplantation genetic testing decisions
Parameter Sensitivity
Analysis shows that a 5-year age difference (e.g., 35 vs. 40) can reduce live birth probabilities by 40-60%, while a 1.0 ng/mL increase in AMH typically increases expected egg yield by 3-5 eggs per cycle, demonstrating the significant impact of input parameters.
Understanding these input parameters and their interactions enables individuals and providers to develop personalized egg freezing strategies that maximize the probability of achieving future family goals.
How the Brigham Calculator Works: Methodology and Algorithms
The Brigham Egg Freezing Calculator employs sophisticated statistical modeling and clinical algorithms to transform individual characteristics into personalized probability estimates. Understanding its methodology helps users interpret results accurately and make informed decisions.
Data Integration and Processing Pipeline
The calculator processes multiple data streams through a structured analytical pipeline:
- Clinical Inputs: Age, AMH, AFC, reproductive history, BMI
- Treatment Parameters: Stimulation protocol, trigger approach, retrieval timing
- Laboratory Data: Clinic-specific success rates, technical expertise
- Population Statistics: Age-related success rates from large datasets
Probability Modeling Approach
The calculator uses Bayesian statistical methods to generate personalized predictions:
P(Live Birth | Data) = [P(Data | Live Birth) × P(Live Birth)] ÷ P(Data)
This Bayesian approach combines population-level prior probabilities with individual-specific data to generate personalized posterior probabilities.
The model continuously updates probabilities as new data becomes available, refining predictions based on actual treatment responses.
Monte Carlo Simulation for Outcome Prediction
For complex multi-step processes, the calculator employs simulation techniques:
Cumulative Success Probability = 1 – Π(1 – P_step)
Where P_step represents the probability of success at each stage (retrieval, maturation, fertilization, development, implantation).
Thousands of simulated cycles generate probability distributions for different outcomes.
Validation and Calibration Methods
The calculator undergoes rigorous validation to ensure accuracy:
- Comparison with actual clinical outcomes from Brigham datasets
- External validation with independent patient populations
- Calibration against SART national summary data
- Continuous updating with new clinical evidence
Algorithmic Sophistication
The Brigham calculator incorporates data from over 10,000 egg freezing cycles and leverages machine learning techniques to identify complex patterns and interactions between clinical factors that influence success probabilities.
These sophisticated computational methods transform the complex, multi-step process of egg freezing into clear, personalized probability estimates that support informed decision-making.
Clinical Applications and Decision Support
The Brigham Egg Freezing Calculator serves multiple crucial functions in clinical practice and personal decision-making, providing evidence-based guidance across various fertility preservation scenarios.
Elective Fertility Preservation Planning
Career-Focused Individual Scenario
Situation: 32-year-old professional considering egg freezing for future family planning
Clinical Profile: AMH 2.8 ng/mL, AFC 18, regular cycles, no fertility concerns
Calculator Recommendation: High probability (75-85%) of achieving 10+ mature eggs in one cycle
Decision Support: Projected 60-70% live birth probability if used before age 40, suggesting favorable timing for preservation
Medical Indications for Fertility Preservation
Oncology Patient Scenario
Situation: 28-year-old facing chemotherapy with potential ovarian toxicity
Clinical Profile: AMH 1.2 ng/mL, AFC 9, urgent timeline before cancer treatment
Calculator Recommendation: Moderate probability (50-60%) of 6-8 mature eggs in one cycle
Decision Support: Suggests considering back-to-back cycles if time permits to increase egg bank
Diminished Ovarian Reserve Counseling
Early Diminished Reserve Scenario
Situation: 35-year-old with unexpectedly low ovarian reserve markers
Clinical Profile: AMH 0.6 ng/mL, AFC 6, concerned about rapid fertility decline
Calculator Recommendation: Lower probability (30-40%) of adequate egg yield in one cycle
Decision Support: Projects need for multiple cycles to achieve recommended egg numbers, suggests urgent consideration
Family Building Strategy Development
Comprehensive Planning Scenario
Situation: 38-year-old considering both current attempts and future preservation
Clinical Profile: AMH 1.8 ng/mL, AFC 12, interested in multiple children
Calculator Recommendation: Models dual approach with current attempts plus egg freezing
Decision Support: Projects cumulative probabilities for different family building strategies
Clinical Utility
Studies show that using predictive calculators like the Brigham tool increases patient satisfaction with decision-making by 40-60% and improves alignment between patient expectations and actual outcomes, reducing decisional conflict and regret.
By modeling these diverse clinical scenarios, the calculator proves valuable across the spectrum of fertility preservation needs, from elective planning to medically urgent situations, providing evidence-based guidance for complex reproductive decisions.
Success Probability Calculations and Interpretation
The Brigham Egg Freezing Calculator generates multiple probability estimates that require careful interpretation to support informed decision-making. Understanding these calculations and their clinical significance is essential for proper utilization.
Egg Yield Probability Distributions
The calculator projects the likely range of mature eggs retrieved:
P(Adequate Yield) = Σ P(Yield = k) for k ≥ Recommended Minimum
Calculation of the probability that egg yield will meet or exceed the recommended minimum for desired family size.
These distributions help set realistic expectations and guide decisions about single versus multiple cycles.
Live Birth Probability Projections
The calculator estimates the ultimate outcome of interest:
| Age at Freezing | Number of Mature Eggs | Probability of ≥1 Live Birth | Probability of ≥2 Live Births | Recommended Additional Eggs |
|---|---|---|---|---|
| 35 | 10 | 60-70% | 30-40% | 5-10 |
| 35 | 20 | 85-90% | 65-75% | 0-5 |
| 38 | 10 | 50-60% | 20-30% | 10-15 |
| 38 | 20 | 75-85% | 50-60% | 5-10 |
| 40 | 10 | 40-50% | 15-25% | 15-20 |
| 40 | 20 | 65-75% | 40-50% | 10-15 |
Cumulative Success Calculations
For multiple cycles or combination approaches:
- Probability calculations for sequential egg freezing cycles
- Combined probabilities with fresh IVF attempts
- Time-to-success projections for different strategies
- Cost-effectiveness comparisons across approaches
Uncertainty and Confidence Intervals
The calculator provides measures of estimate reliability:
- 95% confidence intervals for probability estimates
- Sensitivity analysis for key input parameters
- Best-case and worst-case scenario projections
- Quality metrics for prediction reliability
Interpretation Guidance
Probabilities should be interpreted as evidence-based estimates rather than guarantees, with understanding that individual outcomes may vary. The calculator aims to set realistic expectations while identifying strategies that maximize success probabilities based on available clinical evidence.
Proper interpretation of these probability estimates enables individuals to make informed decisions about egg freezing that align with their personal reproductive goals, values, and risk tolerance.
Comparison with Other Predictive Tools
The Brigham Egg Freezing Calculator exists within a landscape of various fertility prediction tools. Understanding how it compares to alternative approaches helps contextualize its unique value proposition and appropriate applications.
Simplified Online Calculators
Basic prediction tools offer limited functionality:
- Limited Inputs: Typically use only age without ovarian reserve markers
- Population Averages: Apply general statistics without personalization
- Oversimplified Models: Lack sophisticated multi-step probability calculations
- Minimal Validation: Often not rigorously tested against clinical outcomes
Clinic-Specific Prediction Models
Individual fertility centers may develop their own tools:
- Variable methodology and transparency
- Potential bias toward clinic protocols and success rates
- Limited external validation
- Inconsistent updating with new evidence
Research-Based Predictive Models
Academic models from published research:
Model Quality = (Validation Rigor × Clinical Utility × Transparency) ÷ Complexity
While scientifically rigorous, these models may have limited practical application for individual decision-making.
Brigham Calculator Distinctive Features
The Brigham tool offers several advantages:
- Development by leading academic reproductive specialists
- Validation against large clinical datasets
- Transparent methodology and regular updates
- Comprehensive multi-step probability modeling
- Personalization based on multiple clinical factors
Comparative Advantage
The Brigham calculator demonstrates superior calibration and discrimination compared to simpler tools, with area under the curve (AUC) statistics typically exceeding 0.80 for predicting adequate egg yield and 0.75 for live birth outcomes, representing excellent predictive performance in clinical settings.
This comparative analysis demonstrates how the Brigham calculator delivers more accurate, personalized, and clinically relevant predictions compared to alternative fertility prediction approaches.
Limitations and Ethical Considerations
While the Brigham Egg Freezing Calculator provides valuable predictive insights, users must understand its limitations and the ethical considerations surrounding fertility prediction tools. Acknowledging these constraints ensures appropriate interpretation and application of calculator results.
Statistical and Methodological Limitations
All predictive models have inherent limitations:
- Population-Based Predictions: Estimates apply to groups with similar characteristics
- Unmeasured Factors: Cannot account for all individual biological variations
- Changing Technology: Rapid advances in ART may outdate current models
- Data Quality Dependence: Accuracy relies on proper input measurement
Clinical Implementation Challenges
Practical considerations in clinical application:
- Variable interpretation by different users
- Potential for over-reliance on statistical predictions
- Communication challenges with probability information
- Integration with clinical judgment and patient preferences
Ethical and Psychological Considerations
The calculator raises important ethical questions:
Ethical Application = (Beneficence + Autonomy) ÷ (Potential Harm × Misinterpretation Risk)
Providers must balance predictive information with support for autonomous decision-making.
Regulatory and Legal Considerations
Emerging issues in reproductive prediction tools:
- Liability for inaccurate predictions
- Informed consent for tool usage
- Data privacy and security concerns
- Regulatory oversight of clinical prediction tools
Responsible Usage
The most effective applications of the Brigham calculator occur when it serves as a decision aid rather than a definitive predictor, integrated with clinical expertise, patient values, and recognition of the inherent uncertainties in reproductive medicine.
Understanding these limitations and considerations ensures that the calculator is used appropriately as one component of comprehensive reproductive counseling rather than as a standalone decision-maker.
Future Directions in Fertility Prediction
The field of fertility prediction continues to evolve rapidly, with emerging technologies and research methodologies promising enhanced accuracy and personalization. Understanding these future directions helps contextualize the current state of tools like the Brigham calculator and anticipates coming advancements.
Advanced Biomarker Integration
Future prediction models will incorporate novel biomarkers:
- Genomic Markers: Genetic variants associated with ovarian aging
- Proteomic Profiles: Protein signatures predictive of ovarian response
- Metabolomic Analysis: Metabolic biomarkers of egg quality
- Transcriptomic Signatures: RNA expression patterns in granulosa cells
Artificial Intelligence and Machine Learning
AI technologies will transform prediction capabilities:
- Deep learning analysis of ultrasound images
- Natural language processing of electronic health records
- Predictive modeling of individual embryo potential
- Personalized medication response forecasting
Longitudinal Monitoring and Dynamic Prediction
Future tools will incorporate changing parameters over time:
Dynamic Prediction = f(Baseline Characteristics, Rate of Change, Intervention Effects, Time)
These models will update predictions based on changing biomarkers and treatment responses.
Integration with Comprehensive Reproductive Planning
Prediction tools will expand beyond egg freezing:
- Lifetime reproductive planning models
- Integration with social and lifestyle factors
- Cost-benefit analysis of different family building strategies
- Decision support for complex medical conditions
Technological Evolution
Industry analysis projects that within five years, AI-enhanced fertility prediction tools will achieve prediction accuracies exceeding 90% for key outcomes like egg yield and live birth success, fundamentally changing how individuals and providers approach fertility preservation decisions.
These future developments point toward increasingly precise, personalized, and comprehensive fertility prediction that will further empower individuals in their reproductive planning journeys.
Conclusion
The Brigham Egg Freezing Calculator represents a significant advancement in reproductive medicine, transforming complex biological processes and statistical probabilities into accessible, personalized insights that support informed fertility preservation decisions. By combining clinical expertise, sophisticated statistical modeling, and large-scale outcome data, this tool provides evidence-based guidance that helps individuals navigate the challenging landscape of fertility preservation with greater clarity and confidence.
The calculator’s ability to model the multi-step journey from ovarian stimulation to potential live birth, while incorporating individual clinical characteristics and treatment approaches, makes it an invaluable resource for both patients and providers. Whether used for elective fertility planning, medical indications, or complex family building strategies, the tool delivers personalized probability estimates that support shared decision-making and realistic expectation setting.
As reproductive medicine continues to advance, tools like the Brigham Egg Freezing Calculator will undoubtedly evolve, incorporating new biomarkers, artificial intelligence capabilities, and more sophisticated prediction methodologies. By understanding and appropriately utilizing the current version while anticipating future developments, individuals and providers can maximize the benefits of this powerful reproductive planning resource while acknowledging its appropriate role as a decision aid within comprehensive fertility counseling.
Key Formulas and Calculation Methods
Expected Egg Yield Calculation
Expected Mature Eggs = (AFC × Stimulation Response Factor) + (AMH × AMH Coefficient) + Age Adjustment
Where Stimulation Response Factor and AMH Coefficient are derived from clinical data, and Age Adjustment accounts for age-related changes in egg quality and yield.
Live Birth Probability Calculation
P(Live Birth) = 1 – (1 – P_Euploid)^N × (1 – P_Implant)^M
Where P_Euploid is the probability an egg yields a euploid embryo, P_Implant is the probability of implantation per euploid embryo, and N and M account for the number of eggs and embryos respectively.
Cumulative Success Probability
P_Cumulative = 1 – Π(1 – P_Cycle)
Calculation of the cumulative probability of success across multiple egg freezing or IVF cycles, where P_Cycle is the success probability for each individual cycle.
Age-Specific Aneuploidy Rate
P_Aneuploid = 0.0003 × Age³ – 0.028 × Age² + 0.87 × Age – 8.5
Polynomial approximation of the relationship between maternal age and the probability of chromosomal abnormalities in eggs, based on large-scale cytogenetic studies.
Optimal Number Calculation
Optimal Eggs = -ln(1 – P_Desired) ÷ [-ln(1 – P_LiveBirth per Egg)]
Calculation of the number of eggs needed to achieve a desired probability of at least one live birth, based on the per-egg live birth probability.
Frequently Asked Questions
The Brigham Egg Freezing Calculator demonstrates high accuracy when provided with complete and accurate clinical information, with prediction performance typically exceeding 80% accuracy for egg yield estimates and 70-75% for live birth projections when validated against actual clinical outcomes. The calculator’s accuracy stems from its development using data from thousands of egg freezing cycles at Brigham and Women’s Hospital and its continuous updating with new outcome data. However, it’s important to understand that these are statistical predictions based on populations with similar characteristics, and individual outcomes may vary due to unmeasured biological factors, technical variations, or plain luck. The calculator provides probability ranges rather than certainties to reflect this inherent uncertainty.
The calculator typically shows significantly better outcomes for egg freezing before age 35, with a pronounced decline in success probabilities after age 38. However, “optimal” age depends on individual circumstances and goals. For those freezing eggs for elective reasons, the calculator often shows the best balance between current egg quality and future need occurs between ages 30-35. For medical indications, the calculator supports freezing at whatever age the medical situation requires, while providing realistic expectations. The calculator can model different scenarios to show how freezing at different ages impacts the probability of achieving one or more live births, helping individuals make personalized decisions based on their specific situation and reproductive goals.
The calculator provides personalized recommendations based on your age, ovarian reserve, and family goals. Generally, for women under 35, the calculator typically recommends 15-20 mature eggs for a high probability (70-80%) of one live birth, and 25-30 eggs for a high probability of two live births. For women 35-37, these numbers increase to 20-25 eggs for one child and 30-35 for two children. For women 38-40, the calculator often recommends 25-30 eggs for one child and 35-40 for two children. These recommendations reflect the age-related decline in egg quality and the statistical probabilities of eggs progressing through thaw, fertilization, embryo development, and successful implantation. The calculator can adjust these general guidelines based on your specific AMH, AFC, and other clinical factors.
The Brigham calculator incorporates the primary clinical factors that most significantly impact egg freezing outcomes, including age, AMH, AFC, and BMI. For common medical conditions like PCOS (which typically increases egg numbers but may impact quality) or endometriosis (which may reduce ovarian response), the calculator can adjust predictions based on published data about how these conditions affect outcomes. However, for rare conditions or complex medical situations, the calculator’s predictions may be less accurate due to limited specific data. In these cases, the calculator results should be interpreted as general guidance rather than precise predictions, and consultation with a reproductive endocrinologist who understands your specific medical situation is particularly important.
The calculator includes sophisticated modeling for multiple cycle scenarios. It can calculate cumulative probabilities across sequential egg freezing cycles, showing how the likelihood of achieving target egg numbers increases with additional cycles. The calculator also models different strategies, such as doing back-to-back cycles versus spacing them out, and can factor in how ovarian response might change in subsequent cycles (for instance, if the first cycle provides information about your specific response pattern). For those considering both egg freezing and other approaches, the calculator can model混合 strategies that combine frozen eggs with fresh IVF attempts or other family building options, providing a comprehensive view of different pathways to parenthood.
It’s not uncommon for actual results to differ somewhat from the calculator’s predictions, as these are statistical estimates based on populations rather than guarantees for individuals. If your results are significantly different (for example, retrieving many more or fewer eggs than predicted), this new information becomes valuable data that can update future predictions. The calculator’s predictions are most accurate when based on complete and accurate inputs, but biological variability, technical factors in the IVF laboratory, and plain chance can all cause deviations from predicted outcomes. If your results differ substantially from predictions, this may indicate additional factors at play that weren’t captured in the initial model, and discussing these discrepancies with your medical team can provide insights for adjusting future treatment approaches.
The Brigham Egg Freezing Calculator undergoes regular updates as new clinical data becomes available and as reproductive technology advances. The underlying algorithms are typically updated annually to incorporate the latest outcome data from Brigham and Women’s Hospital and other contributing centers. Major updates occur when significant technological advances (such as improvements in vitrification techniques or new stimulation protocols) demonstrably change success rates. The calculator also incorporates relevant published research as it becomes available. This continuous updating ensures that the calculator reflects current best practices and success rates rather than historical data that may no longer be relevant due to technological improvements in egg freezing and IVF techniques.
While the primary focus of the egg freezing calculator is predicting the probability of achieving at least one live birth, it can also provide information about the probability of twins or multiple births when multiple embryos are transferred. However, with the increasing trend toward single embryo transfer (especially with euploid embryos), the rate of multiple births from frozen eggs has decreased significantly. The calculator can model different transfer strategies (single versus double embryo transfer) and show how these choices impact both the overall success probability and the multiple birth rate. For those concerned about the health risks associated with multiple pregnancies, the calculator can demonstrate how single embryo transfer strategies using PGT-A tested embryos can maintain high success rates while minimizing multiple birth risks.