| Table 3. Development of zygotes to blastocysts and blastocyst quality depending on embryo morphology assessed at day three. | ||||
| Embryo morphology | Grade 1 and 2a | Grade 2b | Grade 3 | Grade 4 |
| Number of embryos | 1349 | 712 | 117 | 594 |
| Blastocyst formation rate | 48.0% (a) | 20.5% (b) | 17.1% (c) | 3.2% (d) |
| Number of blastocysts | 648 | 146 | 20 | 19 |
| Proportion of good quality blastocysts | 16.2% (e) | 13% (f) | 10% (g) | 10.5% (h) |
a versus b p<0.0001; 95% CI 23.5 to 31.5
b versus c NS
c versus d p<0.00001; 95% CI 6.9 to 20.9
e versus f, g and h NS
Χ2 test