The use of frozen embryos during in vitro fertilisation (IVF) results in just as many live births as the use of fresh embryos, a new study has found.

With IVF, a woman's eggs are fertilised with sperm outside the body in a laboratory. The resulting embryos are then placed back inside her womb.

If fresh embryos are being used, they will be transferred into the womb a few days later, however people now have the option of also freezing these embryos and using them at a later date.

"Frozen embryo techniques are growing in popularity in fertility clinics worldwide. This is one of the reasons why our research is important for fertility clinicians and researchers, and of course couples who are hoping to have a child," commented the study's lead author, Dr Lan N. Vuong, of the University of Medicine and Pharmacy in Ho Chi Minh City, Vietnam.

Working with researchers in Australia, the team looked at almost 800 women who had infertility that was not related to polycystic ovarian syndrome (PCOS). This is because previous research suggests that frozen embryos result in more live births among those with this condition.

For this study, the women underwent one cycle of IVF, either with a fresh or frozen (and then thawed) embryo. The study found that after one round of IVF, 34% of the women in the frozen embryo group got pregnant and went on to have a child, while in the fresh embryo group, this figure was 32%.

"This new study shows that infertile women not suffering from PCOS have equivalent live IVF birth rates from frozen embryos, which is important news for infertile women worldwide.

"Our key finding is that freezing embryos for IVF is not harming a couple's chances of having a baby. After the first fresh embryo transfer, it will be possible to freeze the remaining embryos and transfer them one by one, which is safe and effective," explained Prof Ben Mol of the University of Adelaide.

Details of these findings are published in The New England Journal of Medicine.