Under the provisions of the German embryo protection law allowing a maximum of only three embryos in culture, blastocyst transfers are underrepresented and for obvious reasons usage of sequential media is not required. This prospective study was set up to evaluate whether a global medium (157 patients) could provide comparable data or even outmatch results achieved with a medium specifically designed for early cleavage stages (116 patients). Though rates of fertilization, cleavage and pregnancy did not differ between both media (P>0.05), interestingly, rate of pregnancy losses was significantly lower in patients with global medium (P<0.01). This led to a significantly higher clinical pregnancy rate (P<0.05). Since patient cohorts were comparable in demographic data and all technical details were kept constant it could be hypothesized that culture conditions and/or culture media could have caused this dilemma.

Keywords: culture conditions, culture media, day 3 transfer, global medium, pregnancy loss