Frozen Two Day 3 Embryos And Subsequently Produced Blastocysts By Vitrification: Advantages For Ivf/Icsi Patients At High Risk Of Ovarian Hyperstimulation Syndrome

Ovarian hyperstimulation syndrome (OHSS) may occur during IVF/ICSI treatment, when fresh embryos transfer is required to be cancelled to avoid OHSS aggravation caused by pregnancy-induced elevation of HCG levels, and all produced embryos should be frozen. However, freezing of day 3 cleavage-stage embryo has shown a low success rate. The purpose of this study was to evaluate the advantages of freezing two day 3 cleavage-stage embryos and subsequently produced blastocysts by vitrification for IVF/ICSI patients at high risk of ovarian hyperstimulation syndrome (OHSS). A retrospective study was conducted among women undergoing IVF/ICSI treatment in a medical university teaching hospital. The clinical pregnancy rate (CPR) and implantation rate (IR) was evaluated in the subjects receiving vitrification and warming of embryos with the CryoLoop system that were at high risk of OHSS. The number of high-quality day 3 embryo per cycle, number of blastocyst per cycle, proportion of blastocysts-freezing cycle, number of day 5 or 6 frozen blastocyst per cycle were significantly higher in the 276 IVF/ICSI patients at high risk of OHSS than controls (P< 0.05). The CPRs for one/two thawed blastocysts transfer and two thawed day 3 embryos transfer were 56.07% and 25.00% per cycle (P< 0.05), and 62.50% and 27.38% per patient, respectively. A significant difference was detected in the IR of day 3 thawed embryos transfer between the two groups (P< 0.05). The strategy of freezing two day 3 embryos and transfer of subsequently produced blastocysts may have more advantage for patients at high risk of OHSS, which produces more high-quality blastocysts, and vitrified-warmed blastocysts transfer in thawed cycles significantly reduces the embryo replacement cycles, and results in excellent implantation and successful pregnancy in a short period of time.