Received February 11, 2012
Accepted March 20, 2012

Objective: To evaluate the interference of laboratory air quality upgrade, from air cleanliness ISO class 7 to ISO class 5, on intracytoplasmic sperm injection (ICSI) results. Methods: Observational, retrospective and comparative study, developed in a private Center for Assistance in Human Reproduction. 228 ICSI cycles were analyzed from January 2006 to December 2009. Cycles performed in ISO class 7 environment were allocated in group ISO7 (n = 97) and those performed in ISO class 5 environment were allocated in group ISO5 (n = 131). Fertilization and cleavage rates, numbers of good embryos and embryos transferred, implantation rate, biochemical and clinical pregnancy were the main outcome measures. Results: Biochemical and clinical pregnancy, and implantation rates (gestational sacs/embryos transferred) were significantly higher in ISO 5 group than in ISO 7 group, even with reduced number of embryos transferred per patient. Women aged ≤ 35 years in ISO 5 group presented with biochemical and clinical pregnancy rates, and implantation rates significantly higher than those in ISO 7 group. Conclusions: This study demonstrated that the upgrade from ISO class 7 to ISO class 5 air quality in the incubation environment shall improve ICSI outcomes. However, air quality does not disregard negative interference of the advanced age on results.