sPTD | Initiation of folic acid supplementation | Â | Unadjusted | Adjusted 1 | Adjusted 2 | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|
 |  | n | HR | (CI) | p | HR | (CI) | p | HR | (CI) | p |
All | No | 964 | 1 | Â | Â | 1 | Â | Â | 1 | Â | Â |
 | 0-8 w preconception | 313 | 0.93 | (0.82; 1.06) | 0.28 | 0.99 | (0.87; 1.13) | 0.89 | 1.01 | (0.88; 1.16) | 0.88 |
 | >8 w preconception | 478 | 1.15 | (1.03; 1.29) | 0.01 | 1.18 | (1.05; 1.32) | 0.005 | 1.20 | (1.06; 1.36) | 0.004 |
Early | No | 169 | 1 | Â | Â | 1 | Â | Â | 1 | Â | Â |
 | 0-8 w preconception | 57 | 0.97 | (0.72; 1.31) | 0.84 | 1.07 | (0.79; 1.45) | 0.67 | 1.04 | (0.76; 1.43) | 0.81 |
 | >8 w preconception | 108 | 1.48 | (1.16; 1.89) | 0.001 | 1.60 | (1.24; 2.06) | <0.001 | 1.55 | (1.18; 2.05) | 0.002 |
Late | No | 795 | 1 | Â | Â | 1 | Â | Â | 1 | Â | Â |
 | 0-8 w preconception | 256 | 0.92 | (0.80; 1.06) | 0.23 | 0.97 | (0.84; 1.11) | 0.63 | 0.99 | (0.86; 1.15) | 0.93 |
 | >8 w preconception | 370 | 1.08 | (0.96; 1.22) | 0.22 | 1.09 | (0.96; 1.24) | 0.19 | 1.12 | (0.98; 1.29) | 0.11 |