Advances in IVF protocol
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advances in IVF protocol 2025 2026 new techniques
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"IVF" AND "embryo selection" AND "artificial intelligence"
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"preimplantation genetic testing" AND "IVF outcomes"
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PMID: 38973269
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PMID: 41202946
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Advances in IVF Protocol
IVF has undergone remarkable evolution since the birth of Louise Brown in 1978. The field has shifted from a single standardized approach to a highly individualized, technology-driven discipline. Here is a structured overview of the major advances.
1. Controlled Ovarian Stimulation (COS): From One-Size-Fits-All to Personalized Protocols
GnRH Antagonist Protocols
The shift from GnRH agonist "long protocols" to GnRH antagonist protocols is one of the most significant changes in COS. Antagonists (e.g., ganirelix, cetrorelix) work by immediate competitive blockade of GnRH receptors, unlike agonists that require initial desensitization over 10-14 days.
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Fixed protocol: Antagonist started on stimulation day 5-6 regardless of follicle size
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Flexible protocol: Antagonist started when a lead follicle reaches 14 mm or estradiol exceeds a threshold
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Advantage: fewer injection days, less ovarian hyperstimulation syndrome (OHSS), and preserved LH activity that may improve oocyte quality
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Katzung's Basic and Clinical Pharmacology, 16th Ed. - GnRH agonists like leuprolide (1 mg/day SC reduced to 0.5 mg/day at menses onset) remain the standard in long protocols; GnRH antagonists have now largely replaced them in routine IVF cycles due to their favorable safety profile.
Progestin-Primed Ovarian Stimulation (PPOS)
Oral progestins (e.g., medroxyprogesterone acetate, dydrogesterone) used during stimulation suppress the endogenous LH surge without injections. This protocol is particularly attractive in resource-limited settings and for patients who prefer oral medication. All embryos are frozen (freeze-all strategy) since the progestin renders the endometrium unreceptive for fresh transfer.
Luteal Phase Stimulation
Previously considered impossible, stimulating follicular growth during the luteal phase is now used in patients with poor ovarian reserve or those needing urgent fertility preservation (e.g., before chemotherapy). Multiple stimulations per cycle ("DuoStim" - follicular + luteal phase in the same cycle) can nearly double the oocyte yield.
2. Triggering Ovulation: GnRH Agonist Trigger
The GnRH agonist trigger (replacing hCG trigger) causes a natural LH/FSH surge that:
- Virtually eliminates severe OHSS (especially important in high responders/PCOS patients)
- Leads to more physiological luteinization
- Must be paired with a freeze-all strategy, as luteal phase support is compromised
A dual trigger (GnRH agonist + low-dose hCG) is now used in patients with empty follicle syndrome or poor oocyte maturation to get the benefits of both agents.
3. Freeze-All Strategy and Vitrification
Vitrification (ultrarapid cryopreservation using high cryoprotectant concentrations) has transformed embryo banking:
- Post-thaw embryo survival rates with vitrification: 93% vs. 76% with slow freezing - Berek & Novak's Gynecology, p. 2046
- This has made the freeze-all strategy practical and widespread
- Benefits of deferring transfer to a subsequent frozen embryo transfer (FET) cycle include:
- Full recovery of endometrial receptivity
- OHSS risk elimination
- Better synchrony between embryo and endometrium
- Genetic testing window (PGT)
A July 2026 Fertility & Sterility systematic review comparing frozen vs. fresh transfer in low responders found nuanced outcomes - freeze-all is not universally superior for all patient subgroups, underscoring the need for individualization.
4. Preimplantation Genetic Testing (PGT)
PGT-A (Aneuploidy)
PGT-A screens all 24 chromosomes via trophectoderm biopsy at the blastocyst stage, selecting only euploid embryos for transfer.
- A 2024 systematic review and meta-analysis of 7 RCTs (Taskin et al., 2024) found no improvement in ongoing pregnancy rates across age groups with PGT-A using comprehensive chromosome screening - but did show a reduction in miscarriage rate across all biopsy types.
- A June 2026 meta-analysis (Hyttel et al., Human Reproduction) examined obstetric and neonatal outcomes - PGT-A remains a tool with ongoing debate over clinical utility outside of recurrent implantation failure and recurrent miscarriage.
PGT-M (Monogenic Disorders) and PGT-SR (Structural Rearrangements)
These are now well-established for families with known heritable conditions (e.g., cystic fibrosis, BRCA mutations, chromosomal translocations) - Emery's Elements of Medical Genetics and Genomics.
Non-Invasive PGT (niPGT)
An emerging frontier: analyzing spent culture medium (cell-free embryonic DNA released during culture) as a proxy for embryo genetics - avoiding the need for biopsy entirely. A 2024 review highlights this as an active area of development still requiring clinical validation.
5. AI and Time-Lapse Embryology
Time-Lapse Incubators
Systems like EmbryoScope allow continuous non-invasive embryo monitoring without removing embryos from stable incubator conditions. Morphokinetic parameters (precise timings of cell divisions) provide additional selection data beyond static Day 5 morphology grading.
Artificial Intelligence in Embryo Selection
A 2026 review in Biology (Mrugacz et al.) and a 2025 review (Olawade et al.) both highlight how AI/machine learning models:
- Automate morphological grading (reducing inter-observer variability)
- Integrate multiple data streams: time-lapse morphokinetics, patient age, previous cycle data, metabolic profiles
- Predict implantation potential with accuracy approaching expert embryologists
A landmark 2026 review in Fertility & Sterility (Racowsky et al., PMID 41202946) calls for a fundamental rethinking of IVF laboratory practice, arguing that automation (dish preparation, denudation, ICSI), adaptive embryo culture, and AI-integrated selection represent the next generation of ART - shifting the field from "tradition-based practice toward a scientifically engineered system."
6. Laboratory Culture Advances
- Sequential vs. single-step media: Modern single-step media allow continuous undisturbed culture to Day 5/6 blastocyst stage
- Oxygen tension: Low-oxygen culture (5% O₂ vs. atmospheric 20%) more closely replicates in vivo conditions and improves blastocyst development
- Microfluidics: Lab-on-chip platforms for sperm sorting (selecting motile, non-DNA-fragmented sperm based on rheotaxis) and even embryo culture in microchannels that mimic fallopian tube fluid dynamics
7. Adjunctive Therapies for Poor Responders
For women with diminished ovarian reserve (DOR):
| Adjunct | Evidence | Dosing |
|---|---|---|
| DHEA | Cochrane review: moderate-quality live birth benefit | 25 mg three times daily for 2-5 months |
| Transdermal testosterone | Cochrane RCT review: moderate benefit in poor responders | 10-12.5 mg for 14-28 days pre-stimulation |
| Growth hormone | Meta-analyses show improved live birth in poor responders | 2.5 mg SC from day 6 of stimulation to trigger |
| CoQ10 | Limited RCT evidence; improves mitochondrial function | 600 mg/day for 2 months prior to cycle |
- Berek & Novak's Gynecology, pp. 2046-2047
8. Endometrial Receptivity and ERA Testing
The Endometrial Receptivity Array (ERA) test uses transcriptomic analysis of endometrial biopsy to identify a patient's precise "window of implantation" - personalizing progesterone timing for FET cycles. Though widely used, ERA remains controversial with ongoing RCTs examining whether truly personalized transfer timing improves live birth rates over standard protocols in unselected populations.
9. Sperm Quality Advances
- ICSI (Intracytoplasmic Sperm Injection): Now used in ~70% of global IVF cycles; a 2024 systematic review (Lokshin et al.) reviews its expanded indications
- IMSI (Intracytoplasmic Morphologically Selected Sperm Injection): High-magnification (~6600x) sperm selection to exclude morphologically abnormal sperm
- MACS (Magnetic-Activated Cell Sorting): Selects against apoptotic sperm using annexin V beads
- AI-assisted semen analysis: Automated systems (CASA 2.0) for precise motility, morphology, and DNA fragmentation profiling
10. Fertility Preservation Advances
- Ovarian tissue cryopreservation and transplantation: Now considered a non-experimental procedure by ASRM for patients facing gonadotoxic treatment
- In vitro maturation (IVM): A 2023 review (Das & Son) reviews IVM's continued relevance - maturing immature oocytes in the laboratory without (or with minimal) stimulation, beneficial for PCOS patients and oncofertility
- Oocyte banking: Vitrified egg banking is now standard of care for elective ("social") fertility preservation
Key Trends Shaping 2025-2026
| Trend | Clinical Impact |
|---|---|
| AI-guided stimulation dosing | Reduces OHSS; optimizes individualized protocols |
| Automation of lab procedures | Reduces human error; standardizes outcomes |
| Segmented IVF (freeze-all) | Decouples stimulation from transfer; improves outcomes in high-risk groups |
| niPGT | May eventually replace invasive biopsy |
| Cumulative live birth rate as primary endpoint | More realistic measure of success across multiple cycles |
| Expanded insurance coverage (US, 2026 ASRM guidelines) | Broadens access for donor gametes and reciprocal IVF |
The field is moving toward an evidence-based, individually tailored, and increasingly automated model of care - a direction summarized well by Racowsky et al. in Fertility & Sterility, 2026 as a shift from "tradition-based to scientifically engineered" assisted reproduction.
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