A study presented at the British Science Festival argues that freezing embryos before implantation in the IVF process results better outcomes for both mother and baby. In the study — done by Dr Abha Maheshwari of Aberdeen University and published in the Fertility Sterility journal — 13,000 IVF pregnancies were studied, and it was found that frozen embryo pregnancies resulted in a third fewer maternal hemorrhages, 16% fewer premature births, and half the chance of infant deaths than in cycles using fresh embryos. One theory is that transferring frozen embryos at a later date allows the stimulated uterus to return to a more natural state. Another is that since only the highest quality embryos make it through the freezing and thawing process, there is a better chance that those embryos will result in healthy pregnancies.
Others, however, argue that there are fewer pregnancies with frozen embryos (approximately 23% success compared to 33% success for fresh cycles), and freezing all embryos before IVF would result in significantly decreased pregnancy rates. Professor Alison Murdoch, the head of the Newcastle Fertility Centre at Life at Newcastle University, stated, “There is ample evidence to show that this would result in fewer pregnancies even if the outcome for those pregnancies were better.”
Though freezing all embryos before IVF transfer may not be warranted yet, at a minimum, the study should reassure the public that frozen embryos are just as safe to use as fresh embryos. As Dr Allan Pacey, the chairman of the British Fertility Society and a researcher at the University of Sheffield put it: “I think this is interesting because some people are nervous about frozen embryos and there have been various headlines about this study or that which suggest that frozen embryos may be a worry. What’s really useful is that it shows that from the point of view of the woman’s health during labour, and some early measures of the baby’s health, frozen embryos do all right and are arguably better.”