Development and evaluation of single sperm washing (SSW) for decontamination in extreme oligospermic HIV positive patients

O2-5% than in O2-20%, (95.2% versus 93.5%, P , 0.05). The mean number of blastomeres on day 2 and 3 was significantly higher in the O2-5% group compared with O2-20% (3.8+1.18 and 3.6+1.13; 6.7+2.09 and 6.2+1.94) P , 0.0001, but embryo morphology (day 2 or 3) was comparable. Significantly more embryos were transferred from the embryos incubated in O2-5% compared to those incubated in O2-20% (33.5% versus 26.6%, respect- ively P , 0.0001), as this group had more "best quality" embryos. Similar frac- tions of embryos were frozen (22.7% in the O2-5% versus 21.5% in O2-20%, NS), thus, relatively less embryos remained for blastocyst culture in the O2- 5% group (40.7% versus 49.4%, P , 0.0001). Blastulation rate was signifi- cantly higher in O2-5% compared with O2-20% (30.8% versus 25.4%, P , 0.05) but no significant difference was found in the number of blastocysts appropriate for freezing (28.6% versus 31.2%, NS). Implantation and preg- nancy rate analysis was carried out only on cycles, which resulted in hom- ogenous O2-5% (n ¼ 124) or O2-20% (n ¼ 80) transfers. Implantation rate was 16.8% and 14.9%, (NS), pregnancy rate was 33.9% and 27.5% (NS) and the corresponding ongoing pregnancy rate was 33.1% and 25.0%, respectively. The Abortion rate was higher in O2-20% but didn't reach statistical significance (2.4% versus 9.1%, NS). Conclusions: This study is the first to substantiate improved IVF results of O2- 5% embryo culture in a large cohort of perfectly matched (sibling) oocytes. Cleavage and blastulation rates were significantly higher in sibling embryos incubated in O2-5% as compared to O2-20%. A larger fraction of good quality embryos was found in the O2-5% group (blastomere number was sig- nificantly higher). A trend for higher implantation, pregnancy and ongoing pregnancy rates were found after transfer of O2-5% embryos.