Table 1.
Summary risk estimates of the overall and subgroup analyses on maternal use of folic acid supplements during pregnancy and risk of autism spectrum disorders in children
| Subgroups | No. (cases) | No. (studies) | Risk estimate (95% CI) | Heterogeneity test I 2 (%) P value | |
|---|---|---|---|---|---|
| All studies | 4514 | 16 | 0.771(0.641–0.928) | 59.7 | 0.001 |
| Study design | |||||
| Prospective | 2794 | 5 | 0.903(0.786–0.998) | 42.6 | 0.138 |
| Case-control | 1720 | 11 | 0.435(0.264–0.717) | 66.0 | 0.001 |
| Ethnicity | |||||
| Asian | 1581 | 8 | 0.669(0.461–0.972) | 64.9 | 0.006 |
| European | 2258 | 3 | 0.844(0.683–0.993) | 53.5 | 0.116 |
| American | 675 | 5 | 0.405(0.165–0.994) | 68.0 | 0.014 |