Table 3 Results of subgroup analysis of post-term birth and autism spectrum disorders (ASD) based on OR
Subgroups | No. of studies | OR (95% CI) | P for Z test | I2 (%) | p for interaction |
|---|---|---|---|---|---|
Study design | |||||
 Cohort | 4 | 1.30(1.23, 1.37) | 0.005 | 98.3 | 0.001 |
 Case–control | 11 | 0.94 (0.88, 1.0) |  < 0.001 | 45.8 | |
Quality of the studies | |||||
 Moderate | 4 | 2.19 (1.14, 3.24) |  < 0.001 | 98.4.0 | 0.001 |
 Low | 12 | 0.94 (0.88, 1.0) |  < 0.001 | 0.0 | |
Child’s gender | |||||
 Male | 3 | 1.37(1.19, 1.56) |  < 0.001 | 0.0 | 0.024 |
 Female | 3 | 1.13(0. 84, 1.43) |  < 0.001 | 0.0 | |
Publication year | |||||
 Before 2000 | 5 | 0.73 (− 0.55, 2.0) | 0.262 | 95.9 | 0.383 |
 After 2000 | 11 | 1.61 (1.13, 2.09) |  < 0.001 | 11 | |
Continent | |||||
 Europe/American | 11 | 1.42 (0.94, 1.90) |  < 0.001 | 96 | 0.778 |
 Asian | 5 | 1.59 (0.7, 2.47) |  < 0.001 | 0.0 | |
Autism diagnoses criteria | |||||
 ICD-8/ICD-9/ ICD-10 | 6 | 1.64 (0.93, 1.99) |  < 0.001 | 97.0 | 0.026 |
 DSM-III, DSM-IV/ DSM-5 | 5 | 2.14 (0.2, 4.08) | 0.031 | 73.3 | |