Table 2. The characteristic of studies were included in the meta-analysis of preterm delivery prevalence in Iran .
| Author | Study location | Type of Study | N (%) | CI 95% |
| Khojaste et al., 201619 | Zahedan | Cross sectional | 227 (19.6) | 14.4-24.8 |
| Akbari et al., 201632 | Esfahan | Cohort | 225 (7) | 3.7-10.3 |
| Gojani et al., 201421 | Rafsanjan | Cross sectional | 5925 (7.5) | 7-14.6 |
| Ajami et al., 201430 | Shahrood | Cross sectional | 4402 (8) | 7.2-8.8 |
| Dolatian et al., 201434 | Tehran | Cohort | 500 (15.5) | 12.3-18.7 |
| Mojibyan et al., 201322 | Yazd | Cross sectional | 205 (13.65) | 9-18.3 |
| Sehhati-Shafaii et al., 201323 | Ardebil | Cross sectional | 3575 (13.6) | 12.5-14.7 |
| Jandaghi et al., 201124 | Ghom | Cross sectional | 10913 (5.6) | 5.2-6 |
| Sohrabi et al., 201125 | Zanjan | Cross sectional | 4528 (7) | 6.3-7.7 |
| Mohsen zadeh et al, 201026 | Khoram abad | Cross sectional | 2179 (8.4) | 7.2-9.6 |
| Tayebi et al., 201036 | Sari | Cohort | 420 (6.2) | 3.9-8.5 |
| Alipure et al., 201033 | Ghom | Cohort | 156 (7.1) | 3.1-11.1 |
| Nematola zadeh et al., 201029 | Tehran | Cross sectional | 512 (10) | 7.4-12.6 |
| Ganji et al., 200927 | Ghom | Cross sectional | 1237 (13.9) | 12-15.8 |
| Shahhosseini et al., 200835 | Sari | Cohort | 262 (10.8) | 7-14.6 |
| Akrami et al., 200637 | Tehran | Cross sectional | 403 (19.85) | 16-23.7 |
| Lotf alizadeh et al., 2005 20 | Yazd | Cross sectional | 1979 (16.4) | 14.8-18 |
| Faramarzi et al., 200528 | Babol | Cross sectional | 3275 (9.6) | 8.6-10.6 |
| Soleymani zadeh et al., 200431 | Bam | Cross sectional | 850 (5.4) | 3.9-6.9 |
Confidence interval