Effect of oxygen concentration on human embryo development evaluated by time-lapse monitoring.

OBJECTIVE: To evaluate, using time-lapse monitoring, the temporal influence of culture in 5% O2 or 20% O2 on human embryonic development.
DESIGN: Retrospective cohort study.
SETTING: University-based fertility clinic. PATIENT(S): In vitro fertilized embryos from women aged <38 years with no endometriosis and ≥8 oocytes retrieved. INTERVENTION(S): Culture in 20% O2 exclusively (group 1), 20% and 5% O2 combined (group 2), or 5% O2 exclusively (group 3). MAIN OUTCOME MEASURE(S): Developmental rates and timing of developmental stages. RESULT(S): The timing of the third cleavage cycle was delayed for embryos cultured in 20% O2 (group 1) compared with embryos cultured in 5% O2 (groups 2 and 3). No difference was observed in timing of the early and full blastocyst stages. More embryos in groups 2 and 3 reached the 8-cell, early blastocyst, and full blastocyst stages than in group 1. We found that embryos in group 3 (5% O2) reached the 8-cell stage faster than embryos in group 2 (5% + 20% O2), but none of the other parameters (i.e., other time points, cumulative development, and embryo score) differed between the two groups. CONCLUSION(S): Culture in 20% O2 reduces developmental rates and delays completion of the third cell cycle. The delayed development after culture in atmospheric oxygen was seen in the precompaction embryo only and therefore appears to be stage specific. CLINICAL TRIAL REGISTRATION NUMBER: NCT01139268.