Design:
Retrospective, observational study.
Chong MK, Ng SH, Sim PK. The Clinical Outcomes of Lasered Assisted Hatching on Single Frozen-Thawed Blastocyst Cycle: A Retrospective, Observational Study. Fertil Reprod 2023;5(4):689. Abstract no. 103. https://doi.org/10.1142/S2661318223744041
Presented: ASPIRE Conference, 2023 | Published: December 2023 | Last reviewed: July 2026
This page summarises findings from a conference abstract published in a peer-reviewed journal, based on clinical data from KL Fertility & Gynaecology Centre. It is presented here for the clinical and scientific community and is not intended as a substitute for individualised patient counselling.
Funding and disclosures: No funding declarations are available for this conference abstract. The authors report no competing interests.
Background and Aims
For an embryo to implant successfully, it must hatch from its outer shell, the zona pellucida, prior to or during implantation. Laser-assisted hatching (LAH) is a procedure in which a 1.46-μm noncontact diode laser creates a small opening in the zona pellucida before embryo transfer, theoretically facilitating hatching and improving the conditions for implantation.
LAH has been proposed as an intervention to increase IVF success rates, particularly for patients with recurrent implantation failure or embryos with a thickened zona pellucida. However, evidence for its benefit in the blastocyst setting has been inconsistent across the literature, with some studies showing benefit in specific populations and others showing no significant effect. The aim of this study was to evaluate the effect of LAH on clinical outcomes, specifically clinical pregnancy rate, miscarriage rate, and ectopic pregnancy rate, in single frozen-thawed blastocyst transfer cycles at KL Fertility & Gynaecology Centre.
Method: Study Design and Patient Population
Subjects:
1,553 single frozen-thawed blastocyst cycles from KL Fertility & Gynaecology Centre, recruited from 2018 to 2022. Mean patient age: 35 ± 0.06 years.
Exclusion criteria:
Gamete or embryo donation cycles, and preimplantation genetic testing (PGT) cases.
Study groups:
LAH group (n=116, 8% of cycles):
LAH performed using a 1.46-μm noncontact diode laser (LYKOS® Laser) prior to embryo transfer.
Non-LAH group (n=1,417, 92% of cycles):
No assisted hatching performed prior to transfer.
Outcome measures:
β-hCG positive rate (per ET), clinical pregnancy rate (intrauterine sac per ET), miscarriage rate (per clinical pregnancy), and ectopic pregnancy rate (per clinical pregnancy).
Note on data: The poster’s combined column header states n=1,553 but the LAH and non-LAH subgroup counts total 1,533 (116 + 1,417). The combined column percentages reconcile with 1,533, suggesting a typographic discrepancy or that 20 cycles contributed to the combined total but were unclassifiable at the subgroup level. The LAH vs. non-LAH group figures are internally consistent and are used as the primary data throughout this summary.
Results: Clinical Pregnancy, Miscarriage, and Ectopic Pregnancy Rates
Table 1. Clinical outcomes by LAH status
Outcome | LAH (n=116) | Non-LAH (n=1,417) | p value |
|---|---|---|---|
β-hCG positive rate | 50.9% (59/116) | 55.8% (790/1,417) | 0.31 |
Clinical pregnancy rate | 44.8% (52/116) | 48.7% (690/1,417) | 0.35 |
Miscarriage rate (per clinical pregnancy) | 17.3% (9/52) | 16.2% (112/690) | 0.86 |
Ectopic pregnancy rate (per clinical pregnancy) | 0% (0/52) | 0.7% (5/690) | — |
No statistically significant difference was found between the LAH and non-LAH groups on any of the three primary outcomes. The absolute differences in clinical pregnancy rate (44.8% vs. 48.7%) and miscarriage rate (17.3% vs. 16.2%) were small and non-significant. No ectopic pregnancies occurred in the LAH group.
Discussion: How These Findings Compare With Published Evidence
The finding of no significant difference in clinical pregnancy or miscarriage rates between LAH and non-LAH blastocyst cycles is consistent with several lines of evidence in the current literature:
- The ALADDIN randomised controlled trial (2024), the largest RCT to date on LAH in vitrified-warmed blastocysts, found no significant improvement in live birth rate following LAH compared with no LAH in an unselected blastocyst population. The authors concluded that LAH should not be used routinely for all blastocyst transfers.
- ESHRE's 2023 good practice recommendations on add-ons in reproductive medicine classify assisted hatching as an intervention for which sufficient evidence of benefit is lacking in the general IVF population, cautioning against routine use outside carefully designed trials or specific high-risk subgroups.
- A 2023 multicentre double-blinded RCT found no benefit of LAH in patients with repeated implantation failure undergoing IVF/ICSI, further challenging the assumption that this is the population most likely to benefit.
- Evidence is more nuanced for specific sub-populations. A 2026 retrospective analysis found that in blastocyst-stage FET, LAH was associated with higher clinical pregnancy and implantation rates, though its effect on live birth rate remained limited, pointing to the predominant influence of maternal factors and embryonic genetic competence at this stage. Benefit from LAH appears more clearly established for cleavage-stage embryos and for those with thick zona pellucida or poor morphology.
Taken together, the literature supports this study’s conclusion that routine LAH does not meaningfully improve outcomes in an unselected blastocyst FET population, while leaving open the possibility of benefit in specific subgroups, principally patients with recurrent implantation failure or embryos with thick zona pellucida — which the current data cannot formally test due to the retrospective, unselected design.
Clinical Significance
These findings do not support the routine use of LAH in all single frozen-thawed blastocyst transfer cycles. However, the study’s conclusion aligns with current clinical practice in suggesting a potential role for LAH in selected patients, specifically those with recurrent implantation failure or embryos with a thick zona pellucida, where the biological rationale for facilitating zona escape is strongest. The finding that LAH did not increase miscarriage or ectopic pregnancy rates is reassuring with respect to its safety profile in this setting.
Limitations of This Case Report
- Retrospective, non-randomised design: allocation to LAH or non-LAH was not random. Clinicians may have preferentially offered LAH to patients with specific clinical characteristics (e.g. prior implantation failure, thick zona), introducing selection bias that cannot be controlled for without stratified data.
- The LAH group (n=116) is substantially smaller than the non-LAH group (n=1,417), limiting statistical power to detect modest differences.
- No live birth data are reported; clinical pregnancy rate is a proxy outcome.
- Blastocyst quality, zona pellucida thickness, number of prior transfer failures, and patient age breakdown are not reported as stratified variables, preventing subgroup analyses in the populations most likely to benefit.
- A 20-case discrepancy between the poster's combined column header (n=1,553) and the sum of the two subgroups (1,533) is unexplained and documented above.
- Conference abstract format; the full dataset and methods are not available for independent review.
- Published as a conference proceedings abstract; not subject to the same peer-review depth as a full original article.
Key Findings
- In 1,553 single frozen-thawed blastocyst cycles, LAH did not significantly improve clinical pregnancy rate compared with no LAH (44.8% vs. 48.7%; p = 0.35).
- Miscarriage rate was comparable between LAH and non-LAH groups (17.3% vs. 16.2%; p = 0.86).
- No ectopic pregnancies occurred in the LAH group (0% vs. 0.7% in non-LAH); this difference was not tested for significance, likely due to very low event numbers.
- These findings do not support routine LAH in unselected blastocyst FET cycles.
- LAH may remain a useful option for patients with recurrent implantation failure or embryos with thick zona pellucida, consistent with current evidence and the study authors' own conclusions.
About the Team Behind This Case Report
- May Kee Chong and Sue Hwee Ng conducted this research as part of the Embryology team at KL Fertility & Gynaecology Centre.
- Poo Keen Sim is the Chief Embryologist and a member of the Scientific Team at KL Fertility & Gynaecology Centre, with over 20 years of hands-on experience in clinical embryology. She holds a Master's degree in Clinical Embryology and is a co-author of this study.
Download the Original Research
Published abstract available at: https://doi.org/10.1142/S2661318223744041 (Fertility & Reproduction, December 2023, Vol. 5 No. 4)
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References
- Chong MK, Ng SH, Sim PK. The Clinical Outcomes of Lasered Assisted Hatching on Single Frozen-Thawed Blastocyst Cycle: A Retrospective, Observational Study. Fertil Reprod 2023;5(4):689. https://doi.org/10.1142/S2661318223744041
- Andre L, Corti L, Reschini M, Restelli L, Guarneri C, Cattaneo A, Alteri A. The effect of laser-assisted hatching on vitrified/warmed blastocysts: the ALADDIN randomized controlled trial. Fertil Steril 2024;122(1). https://doi.org/10.1016/j.fertnstert.2024.02.010
- Curfs B, Cohlen BJ, Slappendel E, Schoot DC, Derhaag JG, van Golde RJT, et al. A multicentre double-blinded randomized controlled trial on the efficacy of laser-assisted hatching in patients with repeated implantation failure undergoing IVF or ICSI. Hum Reprod 2023;38(10):1952-1960. https://doi.org/10.1093/humrep/dead173
- Lacey L, Hassan S, Franik S, Seif MW, Akhtar MA. Assisted hatching on assisted conception (in vitro fertilisation and intracytoplasmic sperm injection). Cochrane Database Syst Rev 2021;3:CD001894. https://doi.org/10.1002/14651858.CD001894.pub6
- ESHRE Add-ons working group, Lundin K, Bentzen JG, Bozdag G, et al. Good practice recommendations on add-ons in reproductive medicine. Hum Reprod 2023;38(11):2062-2104. https://doi.org/10.1093/humrep/dead184