How to optimize culture media osmolality during Assisted Reproductive Technologies treatments.

The objective of our study was to compare the osmolality in sequential and single step culture media, used for in vitro human embryo culture, covered with mineral oil and paraffin, in dry and humid incubators. We performed a prospective observational study. A total of 120 Petri dishes, with 960 droplets of culture media, were evaluated. Each dish was prepared with 4 droplets of single step medium and sequential medium. Sixty dishes were covered with mineral oil and 60 with paraffin oil. Half were incubated in a dry incubator and half in a humid. Osmolality was measured on days 1, 3, 5, 7. ANOVA test was performed for statistical analysis. Osmolality results for single step and sequential medium, that were covered with both mineral and paraffin oil and placed in the dry incubator, significantly increased throughout the study time (D7>D5>D3). In the humid incubator, the results were similar for all periods. Osmolality was significantly lower in humid incubator, in all periods, when droplets were covered with both oils. When both culture media were placed in the humid incubator, no variation was detected, using both oils. However, when single step medium was placed in the dry incubator, covered with mineral oil, we observed a higher osmolality than the covered with paraffin oil. TWe can conclude that humid incubator is better for maintaining osmolality and paraffin oil protect single step media from evaporation in dry incubator.