TABLE 4.
Association of dietary iron and fecundability among women planning a pregnancy in the Snart Foraeldre and PRESTO cohorts, stratified by heavy menses/short cycles1
| Heavy menses or short cycles | Not heavy menses or short cycles | |||||
|---|---|---|---|---|---|---|
| Pregnancies, n | Cycles at risk, n | Adjusted2 FR (95% CI) | Pregnancies, n | Cycles at risk, n | Adjusted2 FR (95% CI) | |
| Snart Foraeldre, n = 1693 | ||||||
| Total iron, mg/d | ||||||
| <10 | 111 | 546 | 1.00 (Ref.) | 312 | 1806 | 1.00 (Ref.) |
| 10–11.9 | 170 | 806 | 1.10 (0.88, 1.37) | 443 | 2289 | 1.11 (0.97, 1.28) |
| ≥12 | 36 | 216 | 0.96 (0.65, 1.41) | 79 | 515 | 0.99 (0.78, 1.27) |
| Heme iron, mg/d | ||||||
| <0.5 | 49 | 259 | 1.00 (Ref.) | 160 | 870 | 1.00 (Ref.) |
| 0.5–0.9 | 209 | 1015 | 0.99 (0.74, 1.33) | 535 | 3017 | 0.98 (0.84, 1.16) |
| ≥1.0 | 59 | 294 | 0.92 (0.64, 1.31) | 139 | 723 | 1.05 (0.85, 1.31) |
| Nonheme iron, mg/d | ||||||
| <9 | 82 | 371 | 1.00 (Ref.) | 241 | 1434 | 1.00 (Ref.) |
| 9–10.9 | 192 | 922 | 1.03 (0.80, 1.33) | 483 | 2580 | 1.15 (0.99, 1.34) |
| ≥11 | 43 | 275 | 0.89 (0.58, 1.35) | 110 | 596 | 1.20 (0.96, 1.51) |
| PRESTO, n = 2969 | ||||||
| Total iron, mg/d | ||||||
| <10 | 77 | 853 | 1.00 (Ref.) | 300 | 1979 | 1.00 (Ref.) |
| 10–11.9 | 133 | 1109 | 1.24 (0.95, 1.63) | 475 | 3201 | 0.94 (0.82, 1.07) |
| ≥12 | 219 | 1396 | 1.57 (1.22, 2.03) | 612 | 3862 | 0.96 (0.85, 1.10) |
| Heme iron, mg/d | ||||||
| <0.5 | 181 | 1387 | 1.00 (Ref.) | 595 | 3875 | 1.00 (Ref.) |
| 0.5–0.9 | 203 | 1457 | 0.97 (0.80, 1.18) | 634 | 4086 | 1.03 (0.93, 1.14) |
| ≥1.0 | 45 | 514 | 0.76 (0.55, 1.05) | 158 | 1081 | 1.12 (0.95, 1.33) |
| Nonheme iron, mg/d | ||||||
| <9 | 58 | 670 | 1.00 (Ref.) | 235 | 1498 | 1.00 (Ref.) |
| 9–10.9 | 135 | 1114 | 1.31 (0.97, 1.78) | 438 | 3002 | 0.87 (0.75, 1.01) |
| ≥11 | 236 | 1574 | 1.54 (1.16, 2.04) | 714 | 4542 | 0.89 (0.77, 1.02) |
1
FR, fecundability ratio.
2
Adjusted for age, vocational training/education, BMI, physical activity, smoking, alcohol consumption, use of oral contraceptives, parity, cycle regularity and length, doing something to improve chances of conception, use of iron and vitamin C supplements, multivitamin use, dietary vitamin C (continuous), and total energy (continuous). The PRESTO models are also adjusted for race/ethnicity. Heme and non-heme iron models are mutually-adjusted for each other.