Number of matched and unmatched cases for each case-control group combination in 1975-81
| Case group | Control group | No of matched cases | No of unmatched cases | No of matched controls |
|---|---|---|---|---|
| Anencephaly | Cardiovascular | 158 | 11 | 469 |
| Anencephaly | Alimentary and urinary | 142 | 27 | 218 |
| Anencephaly | Combined | 163 | 6 | 499 |
| Spina bifida and cranium bifidum | Cardiovascular | 183 | 12 | 404 |
| Spina bifida and cranium bifidum | Alimentary and urinary | 171 | 24 | 299 |
| Spina bifida and cranium bifidum | Combined | 194 | 1 | 730 |
| All neural tube defects | Combined | 348 | 16 | 806 |