Effect of oxygen concentration during the incubation of embryos of women undergoing ICSI and embryo transfer: a prospective randomized study

The hypothesis that ICSI outcome can be improved by culturing human embryos in an atmosphere of controlled O2 concentration (5%) compared with 20% was tested in a prospective randomized study of 712 transfer cycles. The cycle characteristics and the embryology parameters were similar between groups. The embryo qualities were similar with day 2 transfers; however, they were better with day 3 transfers incubated in 5% O2 than in 20% O2. The clinical outcome parameters did not differ between groups according to the O2 concentration. The results indicated that culture of embryos under atmospheric conditions of O2 for the first 2 or 3 days did not alter the clinical outcome in ICSI cycles.