IVF success rates increase while minimising multiple embryo transfers

Improvements in IVF protocols have improved birth rates, while reducing the number of multiple pregnancies, according to research presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) in London.

Twin and higher-order multiple pregnancies are known to pose escalating health risks for both mothers and babies. Researchers in Australia have examined the impact of improvements in IVF techniques to evaluate whether transferring multiple embryos remains a legitimate option to increase IVF success.

'For many years, transferring two embryos increased the chance of pregnancy from any one transfer, but often came with twin pregnancy rates approaching 30 percent,' said Dr Dean Morbeck from Genea Fertility in Sydney, who presented the research. 'What our data show is that this trade-off has largely disappeared.'

The researchers looked at data from nearly 18,400 women who began IVF treatment at seven Australian fertility clinics between 2012 and 2023. Women using donor eggs or previously frozen eggs/embryos were excluded, as were those who needed PGT-M or PGT-SR. They were followed up until a live birth or until the end of three full cycles if no birth occurred.

The cumulative birth rate across three cycles was over 68 percent, with 95.3 percent single-embryo transfers and a multiple-birth rate below three percent. This compares with cumulative birth rates of 53-59 percent in earlier studies, in which multiple births exceeded 20 percent.

Dr Morbeck attributes this improvement to modern IVF laboratory techniques: 'Blastocyst culture... became much more effective with vitrification, which dramatically improved embryo survival after freezing and warming, making frozen embryo transfer outcomes comparable to fresh transfers,' he said. 'Together, these advances enabled approaches such as freeze-all treatment, where embryos are transferred one at a time later, rather than during the initial stimulation cycle.'

The researchers also looked at the data broken down over time. Over the course of the study, the proportion of single embryo transfers increased from 92.8 percent to 97.3 percent, and multiple births fell from 3.2 percent to 2.7 percent.

Across the same time period, the proportion of fertilised eggs that developed into transferable blastocysts increased, which the authors attribute to the introduction of new embryo culture technologies.

'Improvements in IVF are typically driven by steady, incremental advances rather than dramatic breakthroughs,' said Professor Borut Kovacic, chair-elect of ESHRE. 'This study demonstrates that optimising laboratory practices, adhering to evidence-based guidelines and adopting a relatively conservative treatment approach can progressively increase cumulative live birth rates while reducing multiple births – two outcomes that matter most to patients seeking a safe and cost-effective route to parenthood within a single stimulation cycle.'