Abstract: Objective To investigate the relationship between the technical parameters of frozen micro-sperm and the clinical outcomes of in vitro fertilization(IVF)cycle. Methods A total of 118 cycles related to intracytoplasmic sperm microinjection(ICSI)after cryoresuscitation of rare spermatozoa during Jan. 2016 and Dec. 2020 were retrospectively analyzed. The cycles were divided into micro freezing group and conventional freezing group according to the method of freezing; husband ejaculation group, epididymal puncture group and testicular puncture group according to the source of sperm; types Ⅰ, Ⅱ and Ⅲ severe asthenia groups according to the quality of sperm. The general data, laboratory and clinical outcomes were compared. The effects of related parameters on the clinical outcomes were analyzed with multivariate binary Logistic regression. Results (1) General data: there were no significant differences in the age, body mass index(BMI), years of infertility, basal follicle stimulating hormone(FSH), anti-Mullerian hormone(AMH), Gn days, total dosage of Gn, E₂ level on hCG day, number of oocytes retrieved, and number of MⅡ eggs among the groups when the cycles were grouped according to freezing method, sperm source and sperm quality. (2) Laboratory parameters and clinical outcomes: there were no significant differences in the transferable embryo rate or clinical pregnancy rate between the micro freezing and conventional freezing groups, but there were differences in the 2PN rate(P=0.002), 2PN cleavage rate(P=0.036), and the high quality embryo rate(P=0.002)(P<0.05). There were no significant differences in 2PN rate or clinical pregnancy rate among husband ejaculation, epididymal puncture and testicular puncture groups, but there were differences in 2PN cleavage rate(P<0.001), transferable embryo rate(P=0.048)and high quality embryo rate(P=0.002). There were no significant differences in 2PN rate, transferable embryo rate, and high quality embryo rate among the severe oligoasthenia types Ⅰ, Ⅱ, and Ⅲ, but there were significant differences in 2PN cleavage rate(P<0.001), implantation rate(P=0.005), and clinical pregnancy rate(P=0.048)among the three groups. (3) The multivariate binary Logistic regression analysis showed that the relative risk of a poor outcome was 0.287 in type Ⅲ versus type Ⅰ severe oligoasthenospermia groups(OR=0.259, 95%CI: 0.075-0.887, P<0.05). Conclusion Similar clinical pregnancy rates can be obtained by micro freezing and conventional freezing. The source of sperm does not affect the clinical pregnancy rate. A lower clinical pregnancy rate may be caused by very severe oligoasthenoteratozoospermia, and further confirmation with an expanded sample size is needed.

Key words: Frozen sperm, Scarce sperm, Male fertility preservation, Clinical outcomes, Assisted reproductive technology, Micro vitrification freezing