Shelf life of embryo culture media: Buffering potential of media apparently not the determining factor

To investigate if the buffering power of embryo culture media is compromised by expiration. Buffering potential of expired culture media was evaluated by measuring pH values. Fertility Laboratory, the University of Texas Medical Branch, USA. The pH of expired culture media were measured and compared with those of unexpired ones in three experimental conditions: (1) pre-incubation, (2) CO2 incubation and (3) post-incubation. Sequential media, comprising Quinn's advantage fertilization, cleavage and blastocyst media (Sage assisted reproduction products Inc.), were used. The media were divided into expired and unexpired groups, based on the manufacturer's indicated expiration dates. The unexpired group was evaluated in their original condition (first time opened). The expired media bottles underwent more than one opening. The pH of the media was measured sequentially in conditions 1, 2 and 3. The expired media (30–390days) displayed significantly (p