Reduction in exposure of human embryos outside the incubator enhances embryo quality and blastulation rate.

Abstract Embryo quality is strongly dependent on the in-vitro culture environment. Conventionally, IVF/intracytoplasmic sperm injection (ICSI) embryos are examined microscopically every morning (from day 1 to day 6) to assess fertilization, cleavage and embryo quality. Consequently, the frequent exposure to non-optimal conditions outside the incubator may adversely affect embryonic viability and quality. Hence, this study investigated whether reduction of observation frequency outside the incubator can enhance blastocyst formation rate. A total of 285 IVF/ICSI cycles were divided into two groups. Embryos in the control group (103 cycles) were assessed out-of-incubator every day after insemination (day 1 to day 6; six times). In the experimental group (182 cycles), embryos were assessed four times, on days 1, 3, 5 and 6. The total blastocyst formation rate, day-5 blastocyst formation rate, proportion of good blastocysts and number of cryopreserved blastocysts per patient were significantly lower for the control group compared with the experimental group (42.5%, 31.4%, 50.7%, 1.72±1.55 versus 52.6%, 40.7%, 60.1%, 2.64±2.59, respectively, P