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. 2019 Jun 1;149(9):1585–1595. doi: 10.1093/jn/nxz094

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.