With Embryo Transfers, is Fresh Best?

Assisted reproductive technologies (A.R.T.), namely IVF and its science has advanced greatly over the past few years. We can now study the uterine environment as a microcosm and relate the dynamic interactions of the embryo as it begins the implantation process. Emphasis previously was placed on the embryo. Evolving science tells us the endometrium is as important.

Curiously, in our laboratory and now reported in the labs of other IVF facilities, we find the pregnancy rates from cryopreserved embryos is as high, if not higher than those rates reported in women who underwent fresh embryo transfers (egg retrieval was completed in the same cycle as the transfer). Initially, these results were found to be perplexing with the belief that the best behaving embryos would be transferred during the “fresh” cycle leaving high quality but perhaps, not the “best embryos” cryopreserved in reserve.

With embryo transfers, is fresh best? The cryopreserved embryo transfer cycles (frozen embryo transfer {FET}) demonstrate both short term and long term benefits. For the woman, there is greater recovery time from the retrieval and with transfer, hyperstimulation syndrome is eliminated. Interestingly, the resultant fetus fairs well equally with lower risks of prematurity and low-birth weights.

What awaits us are proper randomized-control trials to assess if the paradigm for fresh embryo transfers should shift to cryopreserve all embryos. In this case, women would undergo, as a routine, a cryopreserved embryo transfer cycle (with preparation of the uterus) in a subsequent menstrual cycle. The concept is intriguing. The proof, of course, is in the pudding (higher pregnancy rates); the question remains if the pudding is in the freezer.