Cryopreservation of human embryos: Progress on the clinical use of the technique in human in vitro fertilization

Abstract

Embryo cryopreservation has been studied at Monash University since 1981 and has been available to patients since mid-1983. Of approximately 1200 patients' cycles of in vitro fertilization (IVF), 445 have had excess embryos which they requested to be frozen. To date 205 patients have requested thawing of their embryos and 144 have had frozen-thawed embryos replaced in utero, resulting in 16 pregnancies. Four of these pregnancies aborted, four are ongoing, and eight deliveries have resulted, including one stillbirth at 26 weeks and one set of twins. Analysis of the data collected to date shows that patients with three or more embryos frozen have a significantly higher pregnancy rate than patients with one or two embryos frozen (23 versus 4%, respectively). Embryo viability, but not embryo survival, following freeze-thawing is related to the degree of embryonic fragmentation and the cell stage at freezing. Eight-cell embryos had a significantly higher viability than other cleavage stages. Those resulting in pregnancy tended to be the faster-dividing eight-cell embryos and were undamaged after freezing and thawing. However, when considering all cleavage stages, there was little effect of freezing damage on embryo viability, providing that at least 50% of the cell complement of embryos were intact and the zona pellucida was undamaged. Nor was there any marked effect of the age of embryos postinsemination. It is also possible that patients who were pregnant following the initial embryo replacement on the cycle of IVF treatment are more likely to conceive following replacement of their frozen-thawed embryos.

Fine structure of early human embryos frozen with 1,2 propanediol

“…The freezing method developed by the French group [Lassalle et al, 1985;Testart et al, 19861 for the preservation of early cleaving embryos with PROH in conjunction with human IVF, seems to compare favorably with the slow method initially developed by the Monash group using dimethyl sulfoxide (DMSO) as a cryoprotectant [Mohr et al, 1985;Freemann et al, 1986;Trounson, 19861. The survival of embryos or their blastomeres after cryopreservation and their morphological appearance after thawing and the type of cryoinjury exhibited are comparable in the two systems.…”

Vitrification: an effective new approach to oocyte banking and preserving fertility in cancer patients

“…On the other hand, embryo cryopreservation is a well established methodology in ART, yielding results that have made it a routine part of clinical practice [9][10][11]. This procedure is applicable only to sexually mature women, and consists of the harvesting of mature oocytes, which are then fertilised, and the embryos are subsequently cryopreserved.…”

Morphology and fertilizability of frozen human oocytes

“…Previous studies have shown that human preimplantation embryos at the 2-cell to blastocyst stages may be cryopreserved and result in pregnancies following replacement in utero [Trounson and Mohr, 1983;Mohr et al, 1985;Freeman et al, 1986;Cohen et al, 1986;Quinn and Kerin, 19861. Recently, there has been increasing interest in the cryopreservation of unfertilized oocytes despite the increased technical difficulty in obtaining survival and the possibility of chromosomal damage arising from freezing oocytes at metaphase I1 of meiosis [see Trounson, 19861. There is little information published to date on frozen human oocytes, although a twin birth has been reported by Chen [1986].…”