New embryo transfer research from M. Meintjes and colleagues discussed.(Report)

According to a study from the United States, "The potentially damaging effect of free O-2 radicals to cultured embryos may be reduced by adding scavengers to the culture media or by reducing the incubator O-2 levels. However, lowering the O-2 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 O-2 tension on live birth rates in a predominately Day 5 embryo transfer program. 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% O-2 (atmospheric) or 5% O-2 (reduced) environment. Clinical endpoints monitored were rates of implantation, clinical pregnancy, live birth and blastocyst cryopreservation. Embryos cultured in a 5% O-2 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 ...