THE EFFECT OF OOCYTE MATURITY INDEX ON BLASTOCYST RATE AND PREGNANCY OUTCOMES.

To determine the effect of oocyte maturity index on pregnancy outcomes in fresh and frozen embryo transfers All autologous day 5, non-PGT embryo transfers (ET) from 2017 to 2021 at a single academic fertility center were included. Both fresh and frozen ETs were evaluated based on oocyte maturity index (OMI), defined as the ratio of M2 to total oocytes retrieved. Primary outcomes studied were blastocyst rate (BR) (number of blastocysts per total number of 2PN) in the fresh cycle, clinical pregnancy (CPR), and live birth (LBR) rates. Cycle characteristics collected included: age, BMI, AMH, infertility diagnosis, days of stimulation, baseline E2, E2 and P4 at trigger, endometrial thickness, trigger medication, total oocytes retrieved, number of embryos transferred, and number of embryos cryopreserved. A total of 196 fresh and 480 frozen ETs were included in this study. In fresh ETs, 46 cycles had OMI ≤70% and 150 cycles had OMI >70%. Cycles with OMI ≤70% had a higher baseline E2 (p=0.04), higher E2 at trigger (p=0.04), and a greater number of oocytes retrieved (p=0.0004). Multiple logistic regression controlling for age and significant variables was performed, and CPR were higher in patients with OMI >70% (p=0.005). A prediction model was created using logistic regression assessing all variables associated with positive pregnancy outcome in the fresh cycle. AMH was inversely correlated with ongoing pregnancy rate (OR 0.931, 95% CI 0.861-0.995). Sub-analysis of OMI ≤70%, 71-80% (N=50), 81-90% (N=49), and 91-100% (N=51) showed that OMI is also inversely related to E2 at trigger (p=0.04) and total oocytes (p<0.0001). Additionally, OMI ≤70% had the highest baseline E2 (p=0.01). Between these groups, there were no statistical difference in BR, CPR, or LBR. In frozen ETs, 129 cycles had OMI ≤70% and 351 cycles had OMI >70%. OMI ≤70% had significantly higher BMI (p=0.01), AMH (p=0.002), E2 at trigger (p=0.001), and total oocytes retrieved (p<0.0001). In cycles that were able to proceed to a frozen transfer, OMI ≤70% had higher utilization of leuprolide-only trigger (p=0.03). Between these groups, there were no difference in CPR or LBR. In the sub-analysis, AMH, frequency of HCG trigger, E2 at trigger, and total oocytes retrieved were all inversely related to OMI. Many patients measure their success of IVF stimulation based on the number of oocytes retrieved. Markers of increased ovarian response include higher AMH, E2 at trigger, and number of oocytes retrieved. However, OMI were significantly decreased in cycles with these parameters. Despite these findings, OMI had no effect on blastocyst rate and only had an effect on CPR in the fresh cycle. Although supraphysiologic levels of steroid hormones may negatively affect implantation, this may be overcome by improved OMI. These negative effects also may also be overcome in frozen ETs where OMI did not impact CPR.