Elective frozen replacement cycles for all: ready for prime time?

Conventionally, most in vitro fertilization (IVF) embryos are transferred in fresh treatment cycles with freezing reserved for spare ones. Improvement in cryopreservation facilities over time has encouraged the greater use of this technology with the success rate of frozen replacement cycles approaching that associated with fresh embryo transfer. Data from observational studies suggest that obstetric and perinatal outcomes are better in pregnancies resulting from frozen replacement cycles. In the interests of promoting feto-maternal safety is it therefore time to avoid fresh embryo transfers in IVF, freeze all available embryos and replace them in subsequent cycles? In this article we explore the biological plausibility of this concept, appraise the evidence underpinning it and consider the implications of adopting such a strategy in routine clinical practice. The outcomes of existing randomized trials appear to favour a strategy of frozen embryo transfer, but larger trials are needed before a major change in clinical practice can be considered.