| CASES (n) | % | CONTROL (n) | % | |
| Term | 26 | −84 | 102 | -90 |
| Preterm | 3 | −10 | 6 | -5 |
| Twin | 2 | −6 | 6 | -5 |
| Total | 31 | 100% | 114 | 100% |