A case of oocyte and embryo vitrification resulting in clinical pregnancy

Prospective randomized comparison of human oocyte cryopreservation with slow-rate freezing or vitrification

“…Although one goal of this study was to reduce embryo cryopreservation, there were instances when embryos resulting from oocyte thawing or warming required cryopreservation to maintain a medically sound number of embryos transferred. Such double cryopreserved embryos (cryopreserved as oocytes and as embryos) can establish pregnancies (52,53). However, if one calculates pregnancy efficiency based on number of oocytes thawed or warmed, minus resulting embryo cryopreserved that have the potential of establishing a pregnancy, and divide by number of clinical pregnancies, the resulting values from this study are 16.5 vitrified/warmed oocytes per pregnancy compared with 33.1 frozen/thawed oocytes per pregnancy.…”

Oocyte cryopreservation: is it time to remove its experimental label?

“…In the intervening years, variations to OC methods including changes in sucrose [14][15][16] and sodium [17,18] concentrations in slow freezing media, along with the first report of successful oocyte vitrification [19] and the development of novel cryotools [20][21][22][23] have combined to provide consistently improved survival and pregnancy rates with OC. In addition, although depolymerization of the oocyte's meiotic spindle is known to occur, a number of studies have now shown that the spindle reforms in the majority of oocytes after thawing [24][25][26][27][28][29].…”

The worldwide frozen embryo reservoir: methodologies to achieve optimal results

“…Other recent retrospective reports have provided evidence that vitrification results in higher survival rates as compared to slow freezing, minimal deleterious effects on postwarming embryo morphology, and improvement in clinical outcomes 18,19 . Moreover, the recent report of clinical pregnancy following oocyte and day 3 embryo vitrification suggests that repeat vitrification and warming of oocytes and embryos are possible and can result in pregnancy 20,21 . This possibility has never been reported with slow freezing and highlights the clinical versatility of vitrification techniques.…”

“…Cryopreservation of human embryos by vitrification or slow freezing was evaluated in a recent systematic review by Loutradi et al 16 From the 90 potential studies considered, only four were deemed suitable for analysis 17 . Only two of these studies reported a direct comparison of day 3 cryopreservation with slow freezing and vitrification 20,29 . Zheng et al have shown a significant improvement of embryo survival following vitrification compared to slow freezing using abnormal donated embryos for research.…”

“…12,13 However, a few publications have compared the clinical outcomes obtained with vitrification versus slow freezing, especially for cleavage stage. [14][15][16][17][18][19][20][21][22] Slow freezing actually remains probably the most commonly used method of cryopreservation in human IVF laboratories around the world, although recent studies have reported very high success with vitrification. [15][16][17][18][19][20][21][22][23][24] Cryopreservation of human embryos by vitrification or slow freezing was evaluated in a recent systematic review by Loutradi et al 16 From the 90 potential studies considered, only four were deemed suitable for analysis.…”