Effects of oocyte vitrification on the outcomes of embryo development and transfer
Objective To investigate the effect of vitrified oocytes undergoing intracytoplasmic sperm injection(ICSI)on embryo development and transfer outcomes.Methods A retrospective cohort study was conducted to analyze the clinical data of patients who underwent ICSI in the Reproductive Center of the Third Affiliated Hospital of Zhengzhou University from October 2015 to December 2022.A total of 95 cycles of vitrified oocytes(named vitrified oocyte group)and 5 830 cycles of fresh oocytes(named fresh oocyte group)in the same period were included,ICSI was used in both groups for fertilization.The cycles were matched at 1∶3 with propensity score matching(PSM),then there was 94 cycles in vitrified oocyte group,282 cycles in fresh oocyte group.The vitrified oocyte group was dividied into two-step method subgroup and crossed bridge method subgroup according to vitrification procedures.The fertilization,embryo development and clinical pregnancy outcomes were compared between the two groups.Multiple linear regression was used to analyze the correlates affecting oocyte survival rate.Results After PSM in vitrified oocyte group,the normal fertilization rate[69.59%(572/822)],the normal cleavage rate[95.63%(547/572)],the available embryo rate[74.41%(407/547)],the high-quality embryo rate[36.38%(199/547)],the available blastocyst rate[37.08%(89/240)]and the oocyte utilization rate[37.00%(407/1 100)]were significantly reduced compared with fresh oocyte group[74.26%(1 875/2 525),P=0.009;97.97%(1 837/1 875),P=0.002;84.65%(1 555/1 837),P<0.001;50.08%(920/1 837),P<0.001;51.68%(537/1 039),P<0.001;61.58%(1 555/2 525),P<0.001].The total fertilization rate,the multiple pronucleus fertilization rate and the oocyte damage rate had no significant differences(all P>0.05).The embryo transfer cycles of vitrified oocyte group had similar implantation rate of cleavage embryos,biochemical pregnancy rate,clinical pregnancy rate and early abortion rate compared with fresh oocyte group(all P>0.05),however the number of cleavage embryo transfer was significantly increased(1.91±0.28 vs.1.72±0.45,P=0.001),the late abortion rate was also significantly increased[10.53%(4/38)vs.1.14%(1/88),P=0.048].Between two-step method and crossed bridge method subgroups,there were significant differences in oocyte survival rate[55.95%(188/336)vs.82.98%(634/764),P<0.001],oocyte damage rate[6.38%(12/188)vs.3.00%(19/634),P=0.032],available blastocyst rate[5.08%(13/59)vs.41.99%(76/181),P=0.006]and oocyte utilization rate[26.49%(89/336)vs.41.62%(318/764),P<0.001],there were no significant differences in total fertilization rate,normal fertilization rate,multiple pronucleus fertilization rate,normal cleavage rate,available embryo rate and high-quality embryo rate(all P>0.05).Multiple linear regression analysis showed that controlled ovarian stimulation procedure(β=-19.730,t=-2.06,P= 0.043),number of vitrified oocytes(β=-1.417,t=-3.10,P=0.003)and procedure of oocytes vitrfication(β=33.872,t=5.04,P<0.001)had a statistical effect on oocyte survival rate.Conclusion Vitrification of oocytes has a negative effect on embryo development,the pregnancy outcomes after embryo transfer is similar to fresh oocytes,the perinatal safety remains to be confirmed by further studied.
OocyteVitrificationEmbryo developmentEmbryo transfer
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