Frozen embryos account for three-quarters of Australian IVF births

Three in four IVF babies in Australia and New Zealand are born from frozen embryos, according to the latest annual report from the Australian and New Zealand Assisted Reproduction Database.

Data from 2024 shows that around 70 percent of embryo transfers now involve a previously frozen embryo. Almost 45 percent of initiated fresh cycles resulted in a 'freeze-all' cycle, with all eggs or embryos being frozen for future use. This number is up from just over 30 percent five years earlier.

'Cryopreservation is now so successful that clinics can plan embryo transfers for the best time in a patient's treatment and consider their longer-term hopes for family size,' said Dr Petra Wale, president of the Fertility Society of Australia and New Zealand (FSANZ), which commissioned the report. She added: 'The data shows why this approach is becoming more common: it can improve the chance of success while supporting safe treatment for patients.'

Unlike fresh transfers, when the embryo is placed into the uterus a few days after egg retrieval, frozen transfers can take place at a much later point, allowing patients to first recover from hormone stimulation and offering flexibility around family planning. Frozen transfers are also considered safer in certain circumstances, in particular for women at risk of ovarian hyperstimulation syndrome.  

Wider adoption of frozen transfers reflects improvements in freezing technology. Modern vitrification techniques cool embryos so rapidly that ice crystals have no time to form and damage cells, allowing more embryos to survive freezing and thawing.

In total, the report recorded almost 114,000 IVF cycles in 2024, with one in five initiated cycles leading to a live birth. Success rates are improving, with live birth rates per embryo transfer rising from 28.9 percent in 2020 to 31.1 percent in 2024. In particular, the authors note that the live birth rate for frozen embryo transfers increased substantially during that period, from 31.2 percent to 33.3 percent.

Single embryo transfer also became more widespread, accounting for 95.4 percent of transfers in 2024, up from 93 percent in 2020. As a result, only 2.2 percent of fertility patients experienced a multiple birth, which carries higher risks for both mothers and babies. Of the 20,918 children born through IVF in 2024, 82.5 percent were full-term singletons of a normal weight, close to the 92 percent rate seen across all Australian births.

'Australia and New Zealand have always been world leaders in the field, with our multiple birth rate below five percent for over a decade,' said Dr Simon McDowell, the vice president of FSANZ. 'We have been able to significantly reduce the health risks associated with multiple pregnancies while increasing success rates.'