Table 3.
Relative risks (RRs) with 95% confidence intervals (95% CI) of adequate maternal periconceptional folic acid supplement use (before and during pregnancy) by combining maternal and paternal education in 683,785 pregnancies, Norway, 1999–2010
| Adequate folic acid use | Unadjusted | Adjusted a | |||||
|---|---|---|---|---|---|---|---|
| Maternal education | Paternal education | Yes | No | RR* | 95% CI | RR* | 95% CI |
| Compulsory education | Compulsory education | 2557 | 48,326 | 0.46 | 0.43–0.50 | 0.53 | 0.50–0.57 |
| Intermediate education | 4758 | 52,693 | 0.77 | 0.72–0.81 | 0.76 | 0.72–0.81 | |
| Tertiary education | 1292 | 10,651 | 1.00 | Reference | 1.00 | Reference | |
| Missing information | 208 | 4994 | |||||
| Intermediate education | Compulsory education | 5079 | 43,708 | 0.60 | 0.57–0.62 | 0.66 | 0.64–0.68 |
| Intermediate education | 18,055 | 116,378 | 0.77 | 0.75–0.79 | 0.81 | 0.79–0.83 | |
| Tertiary education | 7477 | 35,269 | 1.00 | Reference | 1.00 | Reference | |
| Missing information | 426 | 3928 | |||||
| Tertiary education | Compulsory education | 3805 | 17,985 | 0.70 | 0.67–0.72 | 0.75 | 0.73–0.77 |
| Intermediate education | 22,150 | 80,373 | 0.86 | 0.85–0.87 | 0.88 | 0.87–0.89 | |
| Tertiary education | 42,541 | 126,896 | 1.00 | Reference | 1.00 | Reference | |
| Missing information | 747 | 3539 | |||||
| Missing data (maternal education) | 28,179 | 1771 | |||||
aAdjusted for paternal age (< 20, 20–24, 25–29, 30–34, 35–39, 40+), year of childbirth (1999–2010 (continuous)), paternal country of origin (Norway, high income countries, low/middle income countries), stratified by maternal education
*p values for interaction between maternal and paternal education were calculated by likelihood-ratio tests (unadjusted p value < 0.001; adjusted p value < 0.001)