Frequency distribution of potential risk factors and crude and adjusted ORs of participation into the NINFEA cohort study
| Potential risk factors | Frequency distribution (%) | Effect on participation (3.1%) | |||
| PBR | NINFEA | Crude OR | Adjusted OR* | 95% CI | |
| Parity (1+) | 43.5 | 21.2 | 0.34 | 0.32 | 0.27 to 0.37 |
| Maternal education (graduate) | 18.1 | 34.1 | 2.42 | 2.30 | 2.02 to 2.62 |
| Smoking during pregnancy | 8.9 | 3.7 | 0.39 | 0.43 | 0.31 to 0.59 |
| Alcohol during pregnancy | 21.5 | 27.4 | 1.39 | 1.32 | 1.15 to 1.51 |
| Infertility treatment | 2.0 | 3.8 | 2.00 | 1.31 | 0.95 to 1.81 |
| Folic acid intake | 80.3 | 85.8 | 1.50 | 1.34 | 1.13 to 1.60 |
| Maternal age (>32 years) | 53.7 | 58.4 | 1.22 | 1.30 | 1.14 to 1.48 |
| Previous miscarriages | 17.5 | 17.7 | 1.02 | 1.10 | 0.93 to 1.29 |
| Low pregnancy weight gain (<10 kg) | 18.6 | 19.6 | 1.07 | 1.10 | 0.95 to 1.29 |
↵* Adjusted for all the other variables in the table.