There is no difference in the live birth rate when embryos are transferred on day five or day three, a multi-centre study in the Netherlands has shown.
The study, of over 1200 women undergoing IVF, carried out across 21 Dutch fertility clinics, sought to determine if waiting until embryos had reached the blastocyst stage (day five) rather than the cleavage stage (day three) to transfer them, made a difference to outcomes. Dr Simone Cornelisse, a researcher and resident in obstetrics and gynaecology at Radboud University Medical Centre, Nijmegen, the Netherlands, presented the results at the annual meeting of the European Society of Human Reproduction and Embryology.
Dr Raj Mathur, consultant gynaecologist and chair of the British Fertility Society, who was not involved in the research told BioNews: 'There has been a move worldwide to culturing embryos to the blastocyst stage, primarily as a means of embryo selection, but concern has been raised that a longer period of embryo culture exposes the embryo to more in vitro risk.
'There is some clinical evidence that pregnancies following the transfer of blastocysts are more likely to be affected by placenta praevia and stillbirth. Hence, the research question asked by Cornelisse et al is an important one for patients and clinicians. Further, the outcome measure they choose (cumulative live birth) is highly relevant.'
Women in the study were randomly assigned to have embryos transferred on either day three or day five. Researchers found of the 603 women who had day five embryos transferred, the cumulative live birth rate was 58.9 percent, compared to 58.4 percent of the 599 women who had day three embryos transferred.
Researchers adjusted their results for maternal age, and found no significant difference between women over or under the age of 36. They did find a trend showing a potential benefit for transferring embryos on day three to women under the age of 36, contrasting to a potential benefit of transferring embryos on day five for women over the age of 36.
This may have been due to underpowering of the study, suggested Dr Cornelisse, who said: 'If we look at this in a larger group of women, the results would probably reach statistical significance.'
The use of fresh and frozen embryos was also compared, with researchers finding an even more marked difference for older women.
'In women aged 36 years or older, with a good prognosis, we saw a clinically relevant higher cumulative live birth rate and live birth rate after transferring fresh embryos, when the embryos were transferred at the blastocyst stage. It is noteworthy that in younger women with a good prognosis, cleavage-stage transfer is a good strategy and just as successful as blastocyst-stage transfer.'
Dr Mathur pointed out the study's limitations: 'For instance, it only applies to treatment cycles where at least four embryos were developing normally on day two. At this stage there is no information on either cost-effectiveness or safety. Patients choosing to use pre-implantation genetic testing do not really have the option of a cleavage stage transfer.
'Further studies will hopefully address some of these issues, but this work provides clinicians useful information to counsel patients in making the right choice for their care.'
Leave a Reply
You must be logged in to post a comment.