A freeze-all cycle is an IVF strategy in which all embryos created in a stimulated cycle are vitrified rather than any being transferred fresh. The fresh transfer is abandoned entirely, and a frozen embryo transfer cycle is planned for a subsequent menstrual cycle or a programmed cycle using hormone preparation.
The rationale for freeze-all is primarily related to the risk of ovarian hyperstimulation syndrome (OHSS). In stimulated IVF cycles, the high levels of follicle-stimulating hormone and oestrogen that produce multiple follicles also make the endometrium less receptive and increase the risk of OHSS if hCG trigger is used. Freezing all embryos and transferring in a subsequent natural or programmed cycle removes the fresh transfer from the high-oestrogen environment of the stimulated cycle.
The published evidence for freeze-all has grown substantially over the past decade. A large randomised controlled trial by Chen et al. (2016) published in the New England Journal of Medicine found significantly higher live birth rates in freeze-all cycles compared to fresh transfer in a polycystic ovary syndrome population. Subsequent meta-analyses have shown benefit in high-responder patients, though the evidence in normal-responder populations is less clear.
<blockquote><p>The growth of freeze-all strategies in UK IVF practice is one of the main drivers of the shift toward frozen embryo transfers accounting for the majority of all IVF treatment cycles. It has also increased the clinical importance of vitrification quality, because in a freeze-all programme, every embryo created must survive cryopreservation before any transfer can occur.</p></blockquote>
The CBS High Security Vitrification Kits and CryoNest storage vessels from Cryolab support freeze-all programmes across UK fertility clinics. Contact us for guidance.
