Hum. Reprod. Advance Access originally published online on October 16, 2008
Human Reproduction 2009 24(2):300-307; doi:10.1093/humrep/den368
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A controlled randomized trial evaluating the effect of lowered incubator oxygen tension on live births in a predominantly blastocyst transfer program
1 Frisco Institute for Reproductive Medicine, Frisco, TX 75034, USA 2 Presbyterian Hospital ARTS Program, Dallas, TX 75231, USA
3 Corresponding address. PO Box 703575, Dallas, TX 75370, USA. Fax: +1-972-382-3093. E-mail: mariusmeintjes{at}aol.com
BACKGROUND: The potentially damaging effect of free O2 radicals to cultured embryos may be reduced by adding scavengers to the culture media or by reducing the incubator O2 levels. However, lowering the O2 in the culture environment can be expensive, troublesome and may not be justifiable. The objective of this study was to evaluate the effect of lowered incubator O2 tension on live birth rates in a predominately Day 5 embryo transfer program.
METHODS: Two hundred and thirty first-cycle women undergoing routine IVF or ICSI with ejaculated sperm were randomized in a prospective clinical trial and stratified for patient age and physician. Embryos of patients were randomly assigned for culture in either a 21% O2 (atmospheric) or 5% O2 (reduced) environment. Clinical endpoints monitored were rates of implantation, clinical pregnancy, live birth and blastocyst cryopreservation.
RESULTS: Embryos cultured in a 5% O2 environment consistently resulted in higher rates of live birth implantation (106/247, 42.9% versus 82/267, 30.7%; difference of 12.2% with 95% confidence interval (CI) of 3.9–20.3, P = 0.005) and live births (66/115, 57.4% versus 49/115, 42.6%; difference of 14.8% with 95% CI of 1.9–27.0, P = 0.043) when compared with rates among women whose embryos were cultured in an atmospheric O2 environment.
CONCLUSIONS: The overall increase in live births demonstrated by this study indicates that the effort and expense to culture embryos in a low-O2 environment is justified. The study was registered at clinicaltrials.gov. NCT00708487 [ClinicalTrials.gov] .
Key words: IVF/human/oxygen/blastocyst/live birth
Partially presented as a poster at the 56th Annual Meeting of the American Society of Reproductive Medicine, San Diego, CA, USA, Fertil Steril 2000;74(Suppl):S256. Submitted on June 24, 2008; resubmitted on September 7, 2008; accepted on September 11, 2008.
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