Modern IVF Shows Stronger Success With Single Embryo TransferIVF.net Newsdesk10 July 2026 |
For many years, one of the central trade-offs in IVF was the balance between success and safety. Transferring more than one embryo could increase the chance of pregnancy from a single transfer, but it also increased the risk of twins and higher-order multiple pregnancies. Those pregnancies carry greater risks for both mother and babies, including preterm birth, low birth weight and pregnancy complications.
A new study presented at the 42nd Annual Meeting of ESHRE suggests that this trade-off has changed substantially in modern IVF practice. Researchers analysed outcomes from 18,396 women undergoing their first IVF cycle between January 2012 and December 2021 across seven Australian fertility clinics, with follow-up through December 2023. The study found that contemporary IVF practice achieved a 68.2 percent cumulative live birth rate over three treatment cycles using optimal per-protocol analysis, while single embryo transfer was used in 95.3 percent of embryo transfers. The multiple birth rate was just 2.9 percent.
These findings are important because they show that high cumulative success rates can be achieved without routinely transferring multiple embryos. Earlier IVF studies, carried out before the widespread use of several now-standard laboratory and clinical practices, reported three-cycle cumulative live birth rates of around 53 to 59 percent, often with multiple pregnancy rates above 20 percent. In contrast, this newer dataset reflects a period in which blastocyst culture, vitrification, freeze-all strategies and optimised frozen embryo transfer protocols had become much more widely embedded in clinical care.
The age-related pattern remained clear. Women under 35 had an optimal cumulative live birth rate of 84.5 percent over three treatment cycles. This fell to 74.4 percent for women aged 35 to 37, 57.7 percent for women aged 38 to 40 and 30.1 percent for women aged 41 to 42. This reinforces a familiar point in reproductive medicine: improvements in IVF laboratory performance can raise overall effectiveness, but they do not remove the biological effect of reproductive ageing.
The study also gives a useful view of how incremental changes in the laboratory may translate into clinical outcomes. Between 2012 to 2015 and 2017 to 2021, the proportion of fertilised eggs developing into usable blastocysts increased from 48.3 percent to 57.6 percent. Over the same period, single embryo transfer increased from 92.8 percent to 97.3 percent, while the multiple birth rate fell from 3.2 percent to 2.7 percent.
This is not a story of one single technology transforming IVF. It is more likely a story of cumulative refinement. Extended embryo culture to day 5 or 6, improved culture systems, lower oxygen environments, reduced embryo handling, more reliable vitrification and better frozen embryo transfer preparation have together changed what clinics can expect from one embryo at a time.
The findings also touch on the role of preimplantation genetic testing for aneuploidy, or PGT-A. In the study, PGT-A was used in one or more treatment cycles in 25 percent of women. However, the overall outcomes were achieved without routine genetic testing for all patients. This does not diminish the value of PGT-A in selected groups, such as patients of advanced maternal age or those with recurrent pregnancy loss, but it does suggest that strong cumulative outcomes are possible in modern IVF programmes without universal use of embryo genetic testing.
For embryologists and IVF laboratories, the message is practical as well as reassuring. The success of single embryo transfer depends on confidence in the full system: stimulation, embryo culture, cryopreservation, warming, endometrial preparation, embryo selection and clinical decision-making. When these elements are well controlled, single embryo transfer can support both high success rates and safer pregnancies.
The study also highlights why cumulative live birth rate is such a useful measure. Patients experience IVF over time, not just as one transfer or one cycle. A single embryo transfer strategy may not always maximise the chance of pregnancy from one isolated transfer, but it can preserve safety while maintaining strong overall chances across a complete treatment pathway.
Modern IVF is increasingly defined not only by whether it can achieve pregnancy, but by whether it can do so safely, consistently and with fewer avoidable complications. This large cohort study supports the view that, in well-developed IVF programmes, single embryo transfer is no longer a compromise. It is becoming a central part of effective, contemporary care.
Sources
8 July 2026. ESHRE
911
