To further investigate the effect of culture medium on foetal growth, a Dutch multicenter randomized controlled trial on the use of two different commercially available culture media was set up: MEDIUM study. This trial is a collaboration between the IVF clinics in Amsterdam (AMC), Groningen (UMCG), Nijmegen (UMCN), Eindhoven (Catharina hospital), Tilburg (Elisabeth hospital) and Maastricht (MUMC). With more than 800 couples enrolled in this study, we will be able to compare the culture media in terms of live birth rate and foetal growth. More information (only available in Dutch).