Table 1. Summary results of the systematic review of the association between young and old father and birth defects.
| Birth defects (Numbers of studies) | Risk | Number of studies | Total number of cases | |
| Young paternal age (<20 years) | Advanced paternal age (≥40 years) | |||
| Urogenital Abnormalities (6) | 5217 | |||
| Increased | 1 | 2 | ||
| Decreased | 0 | 0 | ||
| Digestive System Abnormalities (5) | 5823 | |||
| Increased | 0 | 0 | ||
| Decreased | 0 | 1 | ||
| Nervous System Malformations (9) | 8191 | |||
| Increased | 1 | 4 | ||
| Decreased | 0 | 0 | ||
| Cardiovascular Abnormalities (11) | 32190 | |||
| Increased | 2 | 6 | ||
| Decreased | 1 | 1 | ||
| Facial deformity (13) | 18807 | |||
| Increased | 1 | 4 | ||
| Decreased | 0 | 1 | ||
| Musculoskeletal Abnormalities (14) | 31479 | |||
| Increased | 3 | 3 | ||
| Decreased | 1 | 3 | ||
| Chromosome Disorders (10) | 18108 | |||
| Increased | 2 | 4 | ||
| Decreased | 0 | 2 | ||