A study finds strong evidence that freeze-all protocols are indeed associated with significantly improved IVF outcomes—especially in women over 35, a patient group rapidly becoming the largest and most challenging category of infertility patient.
Conventional IVF protocols involve the transfer of a fresh embryo to the uterus during the same cycle in which the eggs were collected and freezing extra embryos for future use. A novel approach to improving IVF outcomes has recently emerged in which all embryos generated from an egg collection cycle are electively frozen and transferred in a subsequent cycle. This “freeze-all” approach, initially developed as a strategy for minimizing risk of ovarian hysperstimulation syndrome (OHSS) in high risk patients, also addresses concerns that some have raised that the drugs used for ovarian stimulation during IVF may have a negative impact on the uterine receptivity of some patients. In theory, therefore, waiting until a later “natural” cycle for embryo transfer should improve outcomes in these patients; however, evidence supporting this claim is limited.
The study examined more than 16,000 IVF treatment cycles performed at 12 leading fertility centres in the USA. After matching for patient age and other variables (including preimplantation genetic screening) analysis showed that freeze-all IVF was significantly associated with improved ongoing pregnancy rates inpatients over 35 years old (46% in freeze-all vs 33% in fresh cycles).