THE ADJUSTMENT OF OXIDATION REDUCTION POTENTIAL (ORP) LEVELS IN CULTURE MEDIA TO THE OVERALL LEVELS OF FOLLICULAR FLUID PRODUCES SIGNIFICANTLY HIGHER EMBRYO PLOIDY RATES IN PATIENTS: A PROSPECTIVE RANDOMIZED STUDY OF SIBLING OOCYTES.

To explore if the adjustment of the redox potential in culture media to similar ORP values found in follicular fluid of donor oocytes improves both usable blastocysts formation and embryo ploidy rates in infertile patients. This prospective cohort study was performed at Citmer, Reproductive Medicine, Mexico City, Mexico from October 2020 to April 2021 and included 901 zygotes deriving from 1381 inseminated oocytes (65.2%) obtained from 79 subfertile patients undergoing ART (ICSI/IVF) with a mean of age of 36.9 years. The oocytes were stratified according to the sibling oocyte model into two groups; Group 1 consisted of 675 oocytes that were inseminated and cultured until blastocyst stage. The ORP of the culture medium for this group was adjusted by adding a combination of antioxidants (EmbryORP®) every 12 hour to adjust the higher levels of ORP in the culture medium to match the overall ORP levels of follicular fluid from oocyte donors (86.0±14.8mV). Group 2: 673 oocytes were inseminated and cultured in commercial culture medium without ORP adjustment until blastocysts stage. Blastocysts underwent Preimplantation Genetic Testing for Aneuploidies (PGT-A) as following: Group 1: 102 blastocysts were biopsied out of 675 oocytes. Group 2: 100 blastocysts were biopsied out of 673 oocytes. All biopsed day-5/6 blastocysts were analyzed by Next generation Sequencing Technique (NGS). Statistical analysis was performed using t-test after Kolmogorov-Smirnov test for normal distribution. A P-value of P<0.05 was considered significant. No differences (P>0.05) were found in blastulation rates, as well as the rate of biopsied embryos from collected oocytes between the two groups. Group 1: 102 biopsied blastocysts out of 675 oocytes (15.1%) vs. Group 2: 100 blastocysts out of 673 (14.8%), respectively. The blastocyst ploidy rate was significantly (P= 0.0389) higher in the Group 1: 51 euploid embryos out of 102 biopsied (50%) vs. Group 2: 32 out of 100 biopsied (32%)] with a 95% of CI for the mean for the Group 1: 25.14 to 42.99 ±4.4735 and Group 2: 38.35 to 56.71 ±4.6116. The adjustment of the ORP level every 12 hour of the embryo culture to physiological ORP levels in patients undergoing PGT-A may increase the embryonic ploidy rate compared to the culture of embryos in regular embryo culture medium with supraphysiological levels of ORP. These preliminary results may also suggest that an improvement in ploidy rates is not always following an increased number of blastocysts usable for PGT-A analysis.