Oxygen concentration and preimplantation development.

The recent article by Karagenc et al. once again shows that atmospheric oxygen is detrimental to embryo development in vitro. This study demonstrates that zygotes can readily develop into blastocysts under ambient oxygen, but in spite of their morphologically normal appearance, the viability of many of these embryos is compromised, with the most pronounced effect on ICM development. Numerous other studies have reached the same general conclusions, but in spite of the strong body of evidence derived from animal studies against using atmospheric oxygen, the entire human IVF community does not seem to have been convinced to abandon its use for embryo culture. This commentary argues for adoption of low oxygen concentrations as the standard for human embryo culture, at least for blastocyst production.