In the field of assisted reproduction, the number of embryos transferred and the risk of multiple pregnancies have always been variables that need to be carefully considered. At the 42nd ESHRE Annual Conference held in London from July 5th to 8th, 2026, a large-scale multi-cycle cohort study provided new insights.
I. Overview of the Conference
The 42nd European Society of Human Reproduction and Embryology (ESHRE) Annual Conference was held in London from July 5th to 8th, 2026. Over 8,000 professionals attended the conference, making it one of the largest international academic events in the field of reproductive medicine. Key topics of discussion included single embryo transfer, cumulative live birth rates, artificial intelligence-assisted fertility treatment, and personalized fertility management.
II. Key Research Findings: Design and Methodology
This study is a multi-cycle cohort study (conferences summary: L26/O-329), conducted by Dean Morbeck et al. from Monash University in Australia. The study involved 18,396 women who started their first IVF cycle at seven reproductive centers in Australia between January 2012 and December 2021. The average age of these women was 36.2 years, and the follow-up period lasted until December 2023. Only those who used autologous oocytes were included in the study. Donor eggs, frozen eggs, patients with single gene disorders or structural rearrangements, as well as those undergoing surrogacy cycles, were excluded from the study.
| Research Metrics | Results |
| Study Subjects | Key Findings |
As a comparison, previous studies reported an average live birth rate of around 53%–59% over three cycles, with a multiple pregnancy rate of over 20%.
Studies have shown that the cumulative live birth rates vary significantly depending on the age at which treatment begins:
| Age Group | Cumulative Live Birth Rate for Three Treatment Cycles |
| Under 35 years old | 84.5% |
| 35–37 years old | 74.4% |
| 38–40 years old | 57.7% |
| 41–42 years old | 30.1% |
It should be noted that these figures represent the probability of achieving at least one live birth within a maximum of three treatment cycles, after continuous use of available eggs and embryos. They do not correspond to the success rate of a single transplantation.
IV. Technological Evolution: Why Single-Embryo Transplants Are Possible
The study compared data from the years 2012–2015 with those from 2017–2021.
It was observed that several indicators improved simultaneously:| Indicators | 2012–2015 | 2017–2021 |
| Available blastocyst rate | 48.3% | 57.6% |
| Optimal cumulative live birth rate | 67.1% | 69.8% |
| Percentage of single-embryo transfers | 92.8% | 97.3% |
| Multiple births rate | 3.2% | 2.7% |
The researchers attributed this change to improvements in laboratory procedures and clinical practices.blastocyst culture has become more routine instead of exceptional; lower oxygen conditions, specialized incubators, and fewer disruptions during embryo manipulation have been introduced; vitrification technology has significantly improved the survival rate of frozen embryos, making frozen embryo transfer results comparable to those of fresh transfers. As a result, strategies such as full embryo freezing and scheduled individual transfers are now feasible. Researchers also noted that in most cases, the traditional trade-off of transferring two embryos to increase the chances of successful pregnancy is no longer significant in their data.
● European monitoring dataEIM, 2023Preliminary data on the annual treatment cycle): Europe36A country...1,473The home center has completed more than1,150,000 assisted reproductive cycles, resulting in247,021It's a very important baby. Among them, frozen embryo transfer is quite common.401,483One cycle has been completed, exceeding the "fresh cycle" for the first time.158,649Approximately43%; This isESHRERecorded since the start of monitoringThe lowest birth rates for twins and triplets.
● Endometrial thickness and age: A study found that the thickness of the endometrium varies among different age groups. However, the proportion of endometrium that meets the criteria for an ideal "three-line pattern" remains consistent across all age groups.94.7%It has dropped to81.0%This indicates that it is necessary to conduct personalized assessments of the endometrium before transplantation.
● Artificial Intelligence: The meeting discussions suggest that...AIIt can assist embryologists in their work, but it cannot guarantee the successful implantation of embryos.
● Male factors: Environmental factors may affect the quality of sperm.DNATherefore, the assessment of male fertility also receives equal attention.
● Egg donation and age: Relevant discussions indicate that using young donors does not completely eliminate the effects of age-related factors.
VI. An Analysis of the Limitations of These Studies
This study is an observational study. Its conclusions are based on specific subjects and established treatment procedures. Therefore, the results cannot be directly applied to all patients. The final decision regarding the number of embryos to be used in the procedure still needs to be made by reproductive doctors, taking into account each individual's situation. The study results should not be interpreted as..."A single transplantation can achieve a certain level of success rate.".
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