[Clinical application of vitrification freezing of oocytes]

Objective: To evaluate the effect of oocyte vitrification on embryo quality and developmental potential. Methods: From January 2014 to December 2017, 30 cases of oocytes vitrification in the reproductive center of Sir Run Run Shaw hospital were collected as the frozen group, due to failure of sperm extraction or inability to obtain sufficient sperm at the ovum pick-up-day because of oligoospermia or azoospermia. 220 cases of fresh oocytes from the same period were selected as the fresh group. The fertilization rate, embryo rate, pregnancy rate, implantation rate and live birth rate of the two groups were compared retrospectively. Results: The survival rate of oocyte resuscitation was 91.4% (180/197). In the frozen group, 24 cases were transferred with 14 pregnancies, while in the fresh group, 31 cases were transferred with 18 pregnancies. The number of 2PN fertilized eggs, 2PN embryos and 2PN high-quality embryos in the frozen group was significantly lower than that in the fresh group (3.7±2.5 vs 7.3±4.8), (3.3±2.5 vs 7.2±4.8), and (1.2±1.8 vs 2.9±2.7) (all P<0.05). The fertilization rate of the frozen group was 77.2% (115/149) and the high-quality embryo rate was 36.6% (37/101), lower than that of the fresh group 77.6% (1 637/2 109) and 40.9% (651/1 591) (P>0.05).The pregnancy rate of the frozen group was 58.3% (14/24) higher than that of the fresh group 58.1% (18/31), the implantation rate of each mature oocyte and the live birth rate of each mature oocyte were 10.8% (15/138) and 10.8% (15/138), both higher than that of the fresh group 9.6% (21/218) and 8.7% (19/218) (all P>0.05). Conclusions: Vitrification cryopreservation of oocytes may lead to a decrease in embryo quality, but embryo development potential is still considerable. Higher pregnancy rate, implantation rate and live birth rate may be obtained.