TABLE 2.
Prospective studies reporting the association between the indicators of iron status and the risk of GDM1
| Study, year | Comparison groups | Crude OR (95% CI) | Adjusted OR (95% CI) | Covariates |
| SF | ||||
| Tarim et al. (42), 2004 | SF top 50th vs. bottom 50th percentile (≥19.7 vs. <19.7 μg/L) | Not provided (positive association) | Not provided (null association) | Not applicable |
| Chen et al. (43), 2006 | Highest 20% vs. lowest 80% (>131.38 vs. ≤131.38 pmol/L) | 2.05 (1.10, 3.86) | 1.84 (0.95, 3.58) | Age, ethnicity, parity, family history of diabetes, gestational age at blood collection, cigarette smoking, and prepregnancy BMI |
| Zein et al. (57), 2015 | Highest vs. lowest quartile (≥38.5 vs. <13.0 μg/L) | 2.49 (0.53, 10.84) | 1.62 (0.20, 12.95) | Age, BMI, and CRP concentrations |
| Khambalia et al. (48), 2016 | Unit change in SF (μg/L) | 1.60 (1.28, 1.99) | 1.41 (1.11, 1.78) | Age, country of birth, parity, weight, smoking, hypertensive disorders in pregnancy, and CRP concentrations |
| Khambalia et al. (49), 2016 | Iron deficient vs. not based on SF concentration (<12 vs. ≥12 μg/L) | 0.41 (0.23, 0.75) | 0.43 (0.23, 0.78) | Age, gestational age, weight, parity, smoking, insurance type, socioeconomic status, and CRP concentration |
| Bowers et al. (54), 20162 | Highest vs. lowest quintile (median 141.0 vs. 25.0 μg/L) | 2.33 (1.41, 3.84) | 2.22 (1.23, 4.01) | Age, family history of diabetes, physical activity, prepregnancy BMI, CRP concentration, and oxidized LDL |
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 10–14 wk of gestation (≥174.0 vs. ≤77.05 pmol/L) | 2.11 (1.06, 4.20) | 2.43 (1.12, 5.28) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 15–26 wk of gestation (≥119.4 vs. ≤49.6 pmol/L) | 3.06 (1.27, 7.34) | 3.95 (1.38, 11.30) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Soluble transferrin receptor | ||||
| Khambalia et al. (48), 2016 | Unit change in sTfR (nmol/L) | 1.02 (0.99, 1.05) | 1.00 (0.97, 1.03) | Age, country of birth, parity, weight, smoking, hypertensive disorders in pregnancy, and CRP concentration |
| Khambalia et al. (49), 2016 | Iron deficient vs. not based on sTfR concentrations (≥21 vs. <21 nmol/L) | 1.25 (0.82, 1.92) | Not provided | Not applicable |
| Bowers et al. (54), 20162 | Highest vs. lowest quintile (median 2.26 vs. 0.79 mg/L) | 2.10 (1.10, 1.18) | 1.48 (0.82, 2.70) | Age, family history of diabetes, physical activity, prepregnancy BMI, parity, CRP concentration, and oxidized LDL |
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 10–14 wk of gestation (≥33.9 nmol/L vs. ≤22.3 nmol/L) | 1.23 (0.62, 2.46) | 1.00 (0.45, 2.20) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 15–26 wk of gestation (≥35.0 vs. ≤24.2 nmol/L) | 1.23 (0.56, 2.67) | 1.17 (0.49, 2.82) | Age, gestational age, parity education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Serum Iron | ||||
| Behboudi-Gandevani et al. (31), 2013 | Unit change in serum iron (μg/dL) | Not provided | 1.01 (1.00, 1.01) | Age, BMI, education, parity, passive smoking, history of GDM, family history of diabetes, deficient zinc/iron intake, and serum zinc and hemoglobin concentrations |
| Hemoglobin | ||||
| Lao et al. (61), 2002 | Highest 25% vs. lowest 75% (>13.0 vs. ≤13.0 g/dL) | 1.87 (1.18, 2.96) | 1.73 (1.08, 2.78) | Age, BMI, and parity |
| Tarim et al. (42), 2004 | Hemoglobin in top 50th vs. bottom 50th percentile (≥12.2 vs. <12.2 g/dL) | Not provided (positive association) | Not provided (null association) | Not applicable |
| Chen et al. (43), 2006 | Highest 20% vs. lowest 80% (>130 vs. ≤130 g/L) | Not provided | 0.81 (0.36, .81) | Age, ethnicity, parity, family history of diabetes, gestational age at blood collection, cigarette smoking, and prepregnancy BMI |
| Tan et al. (62), 2011 | High vs. low hemoglobin (≥11.5 vs. <11.5 g/dL) | 1.30 (1.1, 1.4) | 1.50 (1.0, 2.1) | Age, ethnicity, height, weight, family history of diabetes, gestational age, red blood cell count, and glycosuria at initial visit |
| Zein et al. (57), 2015 | Hemoglobin in top 50th vs. bottom 50th percentile (≥125 vs. <125 g/L) | Not provided (null association) | Not provided | Not applicable |
| sTfR:SF ratio | ||||
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 10–14 wk of gestation (≥77.84 vs. ≤27.65) | 0.47 (0.22, 1.00) | 0.33 (0.14, 0.80) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 15–26 wk of gestation (≥130.88 vs. ≤40.40) | 0.25 (0.10, 0.64) | 0.15 (0.05, 0.48) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Hepcidin | ||||
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 10–14 wk of gestation (≥18.71 vs. ≤6.97 ng/mL) | 1.32 (0.66, 2.67) | 1.11 (0.51, 2.44) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
| Rawal et al. (55), 20172 | Highest vs. lowest quartile at 15–26 wk of gestation (≥7.92 vs. ≤4.00 ng/mL) | 2.40 (1.08, 5.35) | 2.61 (1.07, 6.36) | Age, gestational age, parity, education, family history of diabetes, and prepregnancy BMI and CRP concentration |
1
CRP, C-reactive protein; GDM, gestational diabetes mellitus; SF, serum ferritin; sTfR, soluble transferrin receptor.
2
Measurements taken in plasma not serum.