Fertilization in vitro of human oocytes by spermatozoa collected in different stressful situations

It has been shown that semen quality is impaired in couplesundergoing in-vitro fertilization (IVF), probably due to stress.A possible effect of stress on the ability of spermatozoa tofertilize human oocytes in vitro was analysed in the presentstudy composed of 26 couples with normozoospermic men undergoingIVF. A semen sample was obtained during the infertility work-upand was cryopreserved (sample 1). A second sample (sample 2)was provided after oocyte retrieval during the IVF cycle. Sample1 was thawed and both samples were washed and preincubated foroocyte insemination. One-hundred-and-five oocytes were inseminatedusing thawed sample 1, and 120 with sample 2.Semen parameterssuch as density, progressive motility and percentage of abnormalforms were compared between sample 1, before and after freezing,and sample 2. Only motility was significantly (P<0.01) decreasedby cryopreservation in sample 1, but no parameter was significantlydifferent when fresh sample 1 was compared to sample 2. Thefertilization rate was 78.6% using sample 1 in comparison to87.5% when sample 2 was employed (not significant, NS). Cleavagerates were 77.7 and 89.7%, respectively (NS). A group of fivepatients undergoing IVF who needed donor semen served as a controlfor the effect of sperm cryopreservation on IVF. In these cases,the donor was asked to provide a fresh sample. Half of thissample was frozen and thawed. Subsequently, fresh and thawedsamples were prepared for insemination and oocytes inseminatedeither with the fresh preparation (n=24) or the frozen and thawedspermatozoa (n=22). There was a significant (P<0.05) decreasein motility in the thawed sample, but fertilization and cleavagerates were not different. These data suggest that the stressfulsituation induced by IVF treatment in normozoospermic men doesnot affect the ability of spermatozoa to fertilize human oocytesin vitro. Cryopreservation of human spermatozoa before IVF maybe a good policy in couples especially suspected of being understress during this procedure.