Freezing all embryos in IVF with transfer in a later, non-stimulated cycle may improve outcome
Source: European Society of Human Reproduction and Embryology (ESHRE), July 2012
There is growing interest in a “freeze-all” embryo policy in IVF. Such an approach, which cryopreserves all embryos generated in a stimulated IVF cycle for later transfer in a non-stimulated natural cycle, would avoid any of the adverse effects that ovarian stimulation might have on endometrial receptivity during the treatment cycle.
Ovarian stimulation has been shown to have adverse effects on endometrial receptivity, and the risk of ovarian hyperstimulation syndrome (OHSS) is also increased when embryo transfer is performed in the stimulated cycle.
Freezing all embryos for later transfer might therefore improve implantation and pregnancy rates and increase the safety of IVF. Presently, the highest success rates in reproductive medicine are seen in the recipients of donor eggs. These are women who have not had ovarian stimulation – their endometrial tissue has not been exposed to high hormone levels, and they are not at risk of OHSS.
However, while the theory of a freeze-all policy seems attractive – and the technique has been commonly employed as a safety measure when OHSS is a threat – no robust systematic studies have indicated whether the cryopreservation of all viable embryos with later frozen embryo transfer (FET) is associated with better outcomes than fresh embryo transfers.