One-step versus two-step culture of mouse preimplantation embryos

Sir, We would like to offer a different perspective on the studyreported by Biggers et al. (2005) whose findings are contradictoryto our own previous studies on these embryo culture media systems. In our previous publication comparing KSOMAA to sequential media(Gardner and Lane, 2002, 2003; Reed et al., 2003), we were carefulto ensure that all conditions used were exactly the same forthe medium being tested, e.g. the same volume of medium. Thiswas done because in our extensive experience, the volume ofmedium has a significant impact on culture outcome if thereare problems with the oil source used. Specifically, when suboptimaloil is used, embryo development increases with increasing volumesof medium. In the