Fig. 2.

Relationship between OCRs of morulae and duration required to develop from morulae to mid-stage blastocysts. Morphological changes from morulae to blastocysts following measurement of OCRs of morulae cultured without mitotoxins were recorded every 10 min. To avoid the effect of maternal age, 6–8-cell stage embryos on day 3 were used from women aged 34–36 years at OPU. Eighteen embryos were donated from 10 couples. The more oxygen morulae consumed, the shorter was the duration required for embryo development between OCR measurement and mid-stage blastocysts (r² = 0.236, P < 0.05). Mid-stage was defined as when the blastocoel reached half the size of the blastocyst