Comparison of continuous and sequential culture media on blastocyst utilization and implantation rates using sibling oocytes

Abstract

The broad availability of commercial embryo culture media has improved performance and consistency in human ART laboratories, however the variety of media compositions from different manufacturers and culture conditions between laboratories has left a lack of consensus across the field. The aim of this study was to provide a carefully controlled comparison of human preimplantation embryo development in two distinct culture media formulations, continuous (Global, Life Global Group) versus sequential (Quinn’s Advantage, Sage). Retrospective, randomized cohort study. A total of 247 fresh non-donor ICSI cycles (2841 oocytes) from January 2014 through April 2015 were included in the analysis. Study inclusion required cohorts of at least six sibling oocytes to be randomly divided into one of two different culture media, continuous (n=1451) or sequential (n=1390). All sibling oocytes and embryos were treated identically regardless of media formulation, including protein supplementation (5mg/mL SPS) and media refreshment on D1 and D3. Culture occurred in Planer mini-benchtop incubators using premixed gas or Thermo cabinet incubators with 6% CO2 and 5% O2. Manufacturer target post-equilibration pH ranges were carefully monitored and varied only slightly between formulations (7.25-7.35 +/-0.05). Rates of fertilization, D5 and D6 blastocyst conversion, embryo transfer (D5), cryopreservation, implantation, and clinical pregnancy were compared. The rate of fertilization post-injection was higher in the continuous media (80%) versus the sequential media (73%; p<0.001). We also observed a significantly higher rate of overall embryo utilization (transfer and cryopreservation) with the continuous media (48% vs 38%; 554/1162 vs 391/1019; p<.0001). This appears to be due in part to a higher rate of D5 blastocyst conversion in the continuous media (33% vs 26%; p<0.001) since D6 conversion rates were not different between the two media formulations (14% vs 12%, p>0.1). Clinical pregnancy and implantation rates for transfers using embryo(s) from a single media (n=37 continuous; n=15 sequential) were not significantly different (65% vs 67%, p=1.0; 53% vs 50%, p=1.0, respectively). Under our laboratory culture conditions, the continuous culture media demonstrated higher fertilization, D5 blastocyst conversion, and utilization rates. However, there was no difference in clinical pregnancy or implantation rates between embryos cultured in continuous or sequential media formulations.