The search for a practice model to reduce miscarriage after assisted reproduction

The analysis of 52,874 clinical pregnancies recorded on the Australian and New Zealand Assisted Reproduction Database (ANZARD) between 2004 and 2008 showed that maternal age and obstetrics history are closely related to the risk of miscarriage, and that the transfer of fresh embryos is associated with fewer miscarriages than transfer of frozen-thawed embryos. It also suggested a higher miscarriage rate is associated with the transfer of thawed blastocysts compared with transfer of thawed cleavage-stage embryos or the blastocysts that ensued from them. Therefore, the authors proposed a practice model of transferring fresh blastocysts and freezing of cleavage-stage embryos to reduce the miscarriage rate after assisted reproduction. This model may have practical limitation and would need validation in a randomized trial. Retrospective analysis of large national databases is useful in identifying trends and generating hypothesis, but evaluation of these hypotheses in randomized trials remains necessary for objective validation.