P–013 Sperm freezing does not affect live birth rates: results from 6,594 cycles in normozoospermic patients
Authors: Torra M , Tutusaus M , Garcia D , Vassena R , Rodríguez A 
Published: August 2021

Abstract

Study question
Does sperm cryopreservation influence the reproductive outcomes of normozoospermic patients undergoing elective ICSI?

Summary answer
After controlling for confounders, the use of cryopreserved semen from normozoospermic patients does not affect pregnancy and live birth rates after ICSI.

What is known already
Sperm cryopreservation with slow freezing is a common practice in ART. While frozen-thawed semen typically presents reduced motility and vitality, its use for ICSI is generally considered adequate in terms of reproductive outcomes. Nevertheless, most studies comparing reproductive outcomes between fresh versus cryopreserved sperm include patients with oligo- and/or asthenozoospermia, where the altered quality of the sample can partially mask the full effect of freezing/thawing. The objective of this study is to ascertain whether ICSI using fresh or cryopreserved semen from normozoospermic patients results in similar fertilization rates and reproductive outcomes.

Study design, size, duration
Retrospective cohort of 6,594 couples undergoing their first elective ICSI cycle between January 2011 and December 2019, using normozoospermic partner semen (fresh or cryopreserved). All cycles involved a fresh embryo transfer, either at cleavage or blastocyst stage. Cycles were divided in 4 groups: fresh semen with partner’s oocytes (FSPO, n = 1.878), cryopreserved semen with partner’s oocytes (CSPO, n = 142), fresh semen with donor oocytes (FSDO, n = 2.413), and cryopreserved semen with donor oocytes (CSDO, n = 2.161).

Participants/materials, setting, methods
A slow freezing protocol using GM501 SpermStore medium (Gynemed, Lensahn) was used for all sperm cryopreservation. Sperm washing, capacitation, and selection prior to ICSI were performed equally for fresh and frozen-thawed samples, using pellet swim-up in IVF® medium (Vitrolife, Göteborg). Fertilization rate (FR), pregnancy (biochemical, clinical, and ongoing) and live birth (LB) rates were compared among study groups using Pearson’s Chi square and Student’s t-test. A p-value &lt;0.05 was considered statistically significant.

Main results and the role of chance
Male and female age, sperm concentration and motility after ejaculation, and number of oocytes inseminated were similar between study groups compared (FSPO vs. CSPO, FSDO vs. CSDO). As expected, oocyte donation cycles resulted in higher LB rate than cycles in which partner’s oocytes were used (30.04% vs 18.17%, p &lt; 0.001). In cycles using partner’s oocytes, no significant differences were observed between fresh and cryopreserved sperm in FR, pregnancy and LB rates (p &gt; 0.05 for all outcomes). However, in oocyte donation, the mean FR after ICSI using cryopreserved semen (73.6 ± 19.6) was lower than the FR obtained with fresh semen (75.1 ± 19.2), p = 0.010. Similarly, in oocyte donation cycles, the biochemical pregnancy rate was significantly lower when using cryopreserved semen (48.5% in CSDO vs. 52.3% in FSDO, p = 0.009), while clinical, ongoing pregnancy and LB rates were similar between both semen status (p &gt; 0.05). In oocyte donation, a subgroup analysis including only the ICSI cycles with embryo transfer at blastocyst stage (n = 1.187 for FSDO, n = 337 for CSDO) confirmed that the LB rate was comparable between fresh and cryopreserved semen groups (34.7% vs 35.6% respectively, p = 0.76), without significant differences in pregnancy rates neither (p &gt; 0.05 for all outcomes).

Limitations, reasons for caution
Caution should be exerted when extrapolating these results to different protocols for sperm cryopreservation and selection, or to IVM and classical IVF cycles, which were excluded from analysis. Due to the retrospective nature of the study, some uncontrolled for variables may affect the results.
Wider implications of the findings: Sperm cryopreservation does not affect pregnancy and live birth rates in normozoospermic patients, although it may lower slightly fertilization rates. In line with previous studies including patients with an apparent male factor detected after routine semen analysis, sperm cryopreservation is a safe and convenient technique.

Trial registration number
Not applicable