Objectives: It has been provided that if incubation time of prepared sperm can affect sperm motility and DNA fragment, but little is known about the influence of sperm preincubation time (SI) on the sperm's fertilizing ability, subsequent embryonic development and pregnancy outcomes in in vitro fertilization (IVF). The aim of this study was to explore the association of SI with fertilization rate, embryo development and clinical outcomes in IVF, further, to find an optimal preincubation time for prepared sperm before insemination in IVF.
Material and methods: This retrospective cohort study included a total of 1453 infertile couples undergoing IVF in our center performed from January 2016 to January 2019. Sperm were preincubated at 37℃ 6% CO₂ for different times before insemination. Preincubation time associated with fertilization rate (FR), 2PN rate, D3 good quality embryo rate, fresh embryo implantation rate (IR), blastocyst formation rate, cumulative pregnancy rate (CPR), cumulative ongoing pregnancy rate (COPR), cumulative live birth rate (CLBR), newborn health and gender ratio were analyzed by chi-square analysis.
Results: FR and 2PN rate of SI more than four hours SI groups (> 4 h SI group) decreased significantly compared with other SI groups (p < 0.01). There were no significant differences of the D3 high quality embryo rate among five SI groups. The blastocyst formation rate of > 4 h SI group was significantly lower than that of 2-3 h SI group (45.5% vs 56.1%, p < 0.05); and 1-2 h SI group also had significant difference with 2-3 h and 3-4 h SI group (48.9% vs 56.1% and 54.6%, p < 0.05). There were a significant decrease of fresh IR and CPR in ≤1 h SI group compared with 1-2 h SI group (19.6% vs. 38.0%, p < 0.05; 62.7% vs 73.7%, p < 0.05); ≤ 1 h SI group also have the lowest CLBR (45.6%), it had statistic differences with 1-2 SI group and 3-4 SI group (45.6% vs 63.2%, p < 0.01; 45.6% vs 61.2%, p < 0.05).
Conclusions: The sperm preincubated time at 37℃ 6% CO₂ before insemination could influence sperm fertilizing ability, blastocyst formation, embryo implantation and CLBR in IVF cycles. The best time for prepared sperm preincubation at 37℃ is one to four hours before insemination in IVF.
Keywords: IVF; cumulative live birth; embryo development; fertilization rate; preincubation time; sperm.