There's no difference between fresh and frozen embryos when it comes to producing IVF babies, Australian and international researchers have found.
A new study has looked at ongoing pregnancy rates and live births in almost 800 women, with one group using frozen embryos, the other fresh. It found no significant difference between the groups.
Professor Ben Mol, from the University of Adelaide's Robinson Research Institute, worked on the study and says it fills a gap in IVF knowledge.
Previous studies have suggested that women with a condition called polycystic ovarian syndrome (PCOS) end up with higher rates of live births when they use frozen, rather than fresh, embryos but just why remains a subject of debate.
But there was no matching data for women struggling to conceive for reasons other than PCOS.
The new study showed ongoing pregnancy occurred in 36 per cent of women in the frozen group, and in 35 per cent in the fresh group. Live birth rates were also on par, at 34 per cent in the frozen group, and 32 per cent in the fresh group.
The research could have a bearing on an emerging trend among many fertility clinics that have been moving away from fresh embryo transfers, in favour of frozen ones.
Prof Mol says there's no benefit in freezing embryos for women who don't have PCOS, and the freezing process can drive up costs.
"Couples concerned about such unnecessary costs of freezing all embryos do not need to go down that path, and will still have the same live birth success rate," he says.
Brisbane woman Christine Flatley went through IVF about five and half years ago, and now has two healthy children, both from frozen embryos that were created at the same time.
"It blows my mind that we have the technology to freeze embryos, then thaw them out years later and enable them to successfully grow into little humans," she says.
"Knowing that my two were effectively conceived at the same time, but then born two and a half years apart is also quite astounding. We are grateful every day for the science that allowed us to have our family."
The study looked only at the common freezing method known as Cryotech vitrification, so the results may not apply to other freezing processes.
It's been published in the latest edition of the New England Journal of Medicine. The study also involved the University of Medicine and Pharmacy in Vietnam's Ho Chi Minh City, and the city's My Duc Hospital.