Table 3. Analysis of effect modification by study characteristics: Prenatal risk factors with heterogeneity (p<0.10).
| Prenatal Risk Factors | Significant Sources of Between-Study Heterogeneity: Study Characteristics (p<0.10) a |
Summary Effect Estimate (95% CI) |
|---|---|---|
| Infections during pregnancy | 1.18 (0.76-1.83) | |
| Multivariate vs. univariate analysis (p=0.09) | ||
| 4 studies: controlled for multiple covariates | 1.82 (1.01-3.30) | |
| 7 studies: no control for covariates | 0.89 (0.56-1.42) | |
| Nausea/Vomiting | 1.16 (0.65-2.09) | |
| Exposure data collection (p=0.004) | ||
| 3 studies: prospective | 1.48 (1.03-2.14) | |
| 3 studies: retrospective | 0.55 (0.31-0.98) | |
| Maternal age: linear trend | none | 1.07 (1.01-1.13) |
| Birth order: linear trend | none | 0.95 (0.89-1.02) |
| Smoking during pregnancy | 1.00 (0.75-1.36) | |
| Population-based (p=0.06) | ||
| 3 studies: population-based | 1.15 (0.90-1.47) | |
| 2 studies: clinic-based | 0.63 (0.37-1.08) | |
| Mother born in another country | none | 1.28 (0.99-1.65) |
| Bleeding | none | 1.81 (1.14-2.86) |
| Toxemia/Preeclampsia, hypertension, swelling |
none | 1.01 (0.80-1.27) |
a
exposure data collection= effect modification by exposure measurement (prospective vs. retrospective) diagnostic criteria = effect modification by diagnostic criteria (narrow vs. broad) multivariate vs. univariate analysis = effect modification by the degree of control for covariates population-based = effect modification by population-based vs. clinic-based sample abnormal = effect modification by use of normal comparison group vs. abnormal comparison group none= no effect modification (p<0.10) by any of the above study characteristics