Humid or dry culture with medium renewal: impact on A-Grade Day 5 Blastocysts. Randomized prospective cohort study

• Published in: Reproductive biomedicine online Vol. 48; p. 104040
• Main Authors: Penas, E. Güell, Espino, E. M. Perulli, Ciurana, V. M. Chapero, Fàbregas, A. Cabré, López, A. Mauri, Pérez, J. I. Mazzanti
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2024
• ISSN: 1472-6483
• DOI: 10.1016/j.rbmo.2024.104040

In recent years, several publications have highlighted the advantages of humid culture (HC) over dry culture (DC) (<45% relative humidity, HR): lower risk of medium evaporation and osmolality changes. The objective of the study was to verify whether the HC of the embryos could have an impact on the development of top-graded blastocysts, this being the first prospective study addressing this aspect through oocytes from the same cohort. We conducted a randomized control trial (RCT) consisting on 379 MII oocytes from 30 patients from August 2022 until January 2024 (and ongoing). After ICSI procedure, sibling oocytes were divided following 1:1 ratio into both humid (>70% HR) and dry (0% HR) chambers of a Geri incubator (Genea Biomedx, Australia). Ejaculated sperm ICSI cycles with >5 fresh MII were included in the analysis. Time-lapse cleavage timings were manually gathered. HC remained undisturbed while medium was renewed on D+3 in DC by changing the culture dish. Fertilization, overall blastocyst development and A-Grade Day 5 blastocysts rates (ASEBIR's morphology criteria) were compared. Statistical analysis consisted on Chi-squared test, t-student test and logistic regression for computation of Odds Ratio (OR, 95%CI). While no statistically significant differences were observed in the fertilization rate (DC: 76.4%; HC: 69.1%, NS) or the overall usable blastocyst development rate (DC: 48.6%; HC: 53.1%, NS), noteworthy distinctions emerged in the proportion of top-graded embryos based on ASEBIR's morphology criteria. Specifically, the A-Grade Day 5 blastocyst development rate displayed significant disparities when comparing all fertilized embryos in each culture type (DC: 19.9%; HC: 32.3%; p<0.05) and also among all usable blastocysts (DC: 40.8%; HC: 60.9%, p<0,05). The Odds Ratio for achieving A-Grade Day blastocysts depending on type of humidity conditions was 1.87 (1,099 – 3,235) for the humid culture. These data highlight that day+3 medium renewal doesn't equalize conditions to humid culture. Ongoing efforts involve validating these insights through an expanded sample size and extensive outcome analysis. Investigating the long-term impact on clinical outcomes and refining culture protocols can amplify the relevance of these findings in assisted reproductive technologies.