Table 3 Characteristics of included case–control studies
Study/ Year of Publication Reference (country) | Participants | Intervention | Outcome | Risk of Bias/Notes |
|---|---|---|---|---|
Correa 2003 [12] USA | Cases were 3278 Infants with congenital malformations related to diabetes. Controls were 3029 infants without congenital malformations. Maternal diabetes and intake of multivitamin were evaluated as a risk factors for congenital malformations | PPC included the use of multivitamin for 3 month before conception | The risk of congenital malformations related to diabetes was limited to infants of f diabetic mothers who had not taken multivitamin (OR 3.39 95% CI 1.79-8.63). Mother who had taken multivitamin had no increase risk of congenital malformations related to diabetes (OR 0.15 95% CI 0.00-1.99) | Medium (clear definition and selection of cases and controls, and outcomes, clearly defined outcome, not clear if the interviewers were blinded to the outcome, recall bias cannot be excluded during the interviews) |