TABLE 3.
Association of dietary iron and fecundability among women planning a pregnancy in the Snart Foraeldre and PRESTO cohorts, stratified by parity1
| Parous | Nulliparous | |||||
|---|---|---|---|---|---|---|
| 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 | 185 | 751 | 1.00 (Ref.) | 234 | 1597 | 1.00 (Ref.) |
| 10–11.9 | 219 | 932 | 1.03 (0.86, 1.24) | 387 | 2156 | 1.18 (1.01, 1.39) |
| ≥12 | 43 | 187 | 1.07 (0.78, 1.46) | 71 | 543 | 0.92 (0.71, 1.20) |
| Heme iron, mg/d | ||||||
| <0.5 | 77 | 333 | 1.00 (Ref.) | 128 | 792 | 1.00 (Ref.) |
| 0.5–0.9 | 290 | 1217 | 0.97 (0.77, 1.23) | 447 | 2808 | 1.00 (0.83, 1.20) |
| ≥1.0 | 80 | 320 | 0.83 (0.62, 1.12) | 117 | 696 | 1.08 (0.85, 1.37) |
| Nonheme iron, mg/d | ||||||
| <9 | 136 | 590 | 1.00 (Ref.) | 183 | 1211 | 1.00 (Ref.) |
| 9–10.9 | 256 | 1063 | 1.18 (0.96, 1.43) | 412 | 2432 | 1.11 (0.94, 1.32) |
| ≥11 | 55 | 217 | 1.32 (0.98, 1.79) | 97 | 653 | 0.97 (0.76, 1.23) |
| PRESTO, n = 2969 | ||||||
| Total iron, mg/d | ||||||
| <10 | 105 | 695 | 1.00 (Ref.) | 272 | 2137 | 1.00 (Ref.) |
| 10–11.9 | 185 | 1065 | 1.00 (0.80, 1.26) | 423 | 3245 | 0.96 (0.83, 1.11) |
| ≥12 | 252 | 1273 | 1.07 (0.86, 1.33) | 579 | 3985 | 1.03 (0.90, 1.19) |
| Heme iron, mg/d | ||||||
| <0.5 | 220 | 1219 | 1.00 (Ref.) | 556 | 4043 | 1.00 (Ref.) |
| 0.5–0.9 | 260 | 1386 | 0.98 (0.83, 1.15) | 577 | 4157 | 1.05 (0.94, 1.17) |
| ≥1.0 | 62 | 428 | 1.02 (0.77, 1.34) | 141 | 1167 | 1.01 (0.84, 1.20) |
| Nonheme iron, mg/d | ||||||
| <9 | 73 | 542 | 1.00 (Ref.) | 220 | 1626 | 1.00 (Ref.) |
| 9–10.9 | 187 | 1020 | 1.21 (0.93, 1.58) | 386 | 3096 | 0.86 (0.74, 1.01) |
| ≥11 | 282 | 1471 | 1.17 (0.91, 1.50) | 668 | 4645 | 0.97 (0.84, 1.12) |
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.