Low-oxygen compared with high-oxygen atmosphere in blastocyst culture, a prospective randomized study

Area of Science:

• Reproductive Medicine
• Embryology
• In Vitro Fertilization

Background:

• Optimizing blastocyst culture conditions is crucial for improving in vitro fertilization (IVF) success rates.
• Oxygen concentration is a key environmental factor that can influence embryo development and viability.
• Previous studies suggest that high oxygen levels may be detrimental to embryo development.

Purpose of the Study:

• To compare the effects of two different oxygen concentrations on blastocyst development and birth rates in IVF.
• To determine if a low-oxygen (5%) environment is superior to a high-oxygen (19%) environment for blastocyst culture.

Main Methods:

• A randomized trial was conducted at a private IVF clinic involving 600 women undergoing IVF.
• Participants were randomized to blastocyst culture in either a two-gas system (6% CO2, 19% O2) or a three-gas system (6% CO2, 5% O2, 90% N2).
• The primary outcome measure was the birth rate.

Main Results:

• A total of 396 women met the inclusion criteria for blastocyst culture.
• The three-gas system (5% O2) resulted in significantly higher blastocyst rates (47.8% vs. 42.1%), more blastocysts per culture (3.8 vs. 3.3), and more cryopreserved blastocysts (1.7 vs. 1.1) compared to the two-gas system (19% O2).
• The birth rate was significantly higher in the three-gas system group (42% vs. 32%), representing a 10% relative increase.

Conclusions:

• Blastocyst culture in a low-oxygen (5%) environment significantly improves blastocyst development and increases birth rates compared to a high-oxygen (19%) environment.
• The findings suggest that reduced oxygen levels mitigate the generation of cytotoxic reactive oxygen species during prolonged embryo culture, thereby enhancing blastocyst viability.
• This study provides evidence for optimizing oxygen concentrations in IVF protocols to improve patient outcomes.