Table 2.
Fetal development after implantation and neonatal birth characteristics of thawed embryos vitrified with a closed or open vitrification system in hormone-replacement cycles
| Closed vitrification | Open vitrification | P- value | |
|---|---|---|---|
| Detection of heart beat (%) | 89.3 (n = 150) | 89.5 (n = 266) | 0.965 |
| Miscarriage rate (%) | 22.0 (n = 150) | 22.2 (n = 266) | 0.966 |
| Stillbirth rate (%) | 0.7 (n = 150) | 0.0 (n = 266) | 0.183 |
| Proportion of monozygotic twins (%) | 0.0 (n = 150) | 0.8 (n = 266) | 0.288 |
| Live birth rate (%) | 75.3 (n = 150) | 77.4 (n = 266) | 0.626 |
| Missing information (%) | 2.0 (n = 150) | 0.4 (n = 266) | 0.104 |
| Mean gestational age (days, mean ± SE) | 275.6 ± 1.4 (n = 113) | 274.1 ± 1.2 (n = 206) | 0.413 |
| Proportion of births before 32 weeks (%) | 2.7 (n = 113) | 1.0 (n = 206) | 0.248 |
| Proportion of births from 32 to 34 weeks (%) | 0.9 (n = 113) | 1.9 (n = 206) | 0.469 |
| Proportion of births from 34 to 37 weeks (%) | 3.5 (n = 113) | 4.9 (n = 206) | 0.585 |
| Proportion of births at normal gestational age (259–293 days) (%) | 92.0 (n = 113) | 89.8 (n = 206) | 0.516 |
| Proportion of births over 42 weeks (%) | 0.9 (n = 113) | 1.9 (n = 206) | 0.469 |
| Mean birth weight (g) | 3127.9 (n = 113) | 3056.8 (n = 206) | 0.227 |
| Birth weight less than 1500 g (%) | 1.8 (n = 113) | 1.5 (n = 206) | 0.826 |
| Birth weight between 1500 and 2500 g (%) | 6.3 (n = 113) | 7.3 (n = 206) | 0.723 |