Low-oxygen compared with high-oxygen atmosphere in blastocyst culture, a prospective randomized study.
OBJECTIVE
To investigate birth rates with two oxygen (O(2)) concentrations in blastocyst culture.


METHODS
Randomized trial.


METHODS
Private in vitro fertilization (IVF) clinic.


METHODS
Six hundred women undergoing IVF.


METHODS
Blastocyst culture in atmospheres with either 6% carbon dioxide (CO(2)) in air, the equivalent to 19% O(2), a two-gas system; or 5% O(2), 6% CO(2), and 90% nitrogen (N(2)), a three-gas system.


METHODS
Birth rate.


RESULTS
The inclusion criterion for blastocyst culture (at least five fertilized oocytes) was fulfilled in 396 women, randomized to 197 cultures with the three-gas system and 199 cultures with the two-gas system. The outcome with the three-gas system compared with the two-gas system showed a statistically significantly increased blastocyst rate (47.8% vs. 42.1%), mean number of blastocysts (3.8 vs. 3.3), and number of cryopreserved blastocysts (1.7 vs. 1.1). The mean number of transferred blastocysts was 1.2 versus 1.3. Culture with the three-gas system increased the relative birth rate by 10% compared with the two-gas system (42% vs. 32%, respectively), a statistically significant difference. The overall twin rate was 4.8%.


CONCLUSIONS
Blastocyst culture with low-oxygen (5%) versus high-oxygen (19%) concentration yielded a better blastocyst outcome and a marked improvement in birth rate. Generation of cytotoxic reactive oxygen species with prolonged embryo culture might deteriorate blastocyst viability.
In Vitro Fertilization Unit, Falun Hospital, Falun, Sweden. urban.waldenstrom@ltdalarna.se
Urban
U
Waldenström
Ann-Britt
AB
Engström
Dan
D
Hellberg
Staffan
S
Nilsson
D000022:Abortion, Spontaneous / Q000453:epidemiology; D000328:Adult; D001755:Blastocyst / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D002245:Carbon Dioxide / Q000494:pharmacology; D018929:Cell Culture Techniques / Q000379:methods*; D004624:Embryo Transfer / Q000706:statistics & numerical data; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005306:Fertilization / Q000187:drug effects / Q000502:physiology; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D009584:Nitrogen / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism* / Q000494:pharmacology; D010101:Oxygen Consumption; D036801:Parturition / Q000502:physiology; D011247:Pregnancy; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods
D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen