| Factor | n (%) |
| Gestational age at admission (week) | 24.9 ± 2.58 |
| The average number of cervical openings (mm) | 17.7 ± 9.92 |
| Cervical openings > 10 mm - < 20 mm | 16 (44.4) |
| Cervical openings < 20 mm | 12 (33.3) |
| Cervical openings < 30 mm | 5 (13.9) |
| Cervical openings ≤ 40 mm | 3 (8.4) |
| Average cervical lengths (mm) | 13.17 ± 5.25 |
| Bulging of fetal membranes (yes) | 21 (58.33) |
| Uterine activity before cervical cerclage | 3 (8.33) |
| Average gestational age when cerclage (weeks) | 25.56 ± 2.53 |