The so-called 'freeze-all' strategy has become increasingly popular in many fertility clinics as frozen embryo transfer is thought to reduce the risk of Ovarian Hyperstimulation Syndrome (OHSS) and improve IVF outcomes generally.
'We found there's no indication for freeze-all embryo transfer for regular cycle women with no risk for OHSS,' said Dr Sacha Stormlund from Copenhagen University Hospital in Denmark. She presented the results of the large, randomised, controlled clinical trial at the annual meeting of the European Society for Human Reproduction and Embryology in Vienna, Austria on Monday.
In the study, some 460 patients at eight clinics across Denmark, Sweden and Spain had a single blastocyst transferred for IVF. A freeze-all approach was used in one group, with the frozen embryo transferred in a subsequent cycle. Fresh embryos were transferred in the other group.
The ongoing pregnancy rate following transfer was similar with both methods, as was the number of babies born through each method.
'I think we can now reasonably say, based on our results and those from other recent trials, that in normally ovulating patients there is no apparent benefit from a freeze-all strategy in IVF,' said Dr Stormlund.
'However, the evidence derived from another large trial in women with polycystic ovary syndrome and at risk of responding excessively to stimulation suggests a considerable freeze-all benefit both in terms of live birth and ovarian hyperstimulation syndrome.'
A spokesperson for the UK's Human Fertilisation and Embryology Authority said: 'Our most recent figures show that the use of frozen embryos has gone up by 11 percent since 2016, which indicates an increased uptake in freeze cycles.
'Frozen cycles' success rates at 23 percent have overtaken fresh embryo cycles' success rates (22 percent) for the first time since records began, meaning that patients can be reassured that freezing embryos can give them as much chance of success as fresh cycles.'