Table 3.
Stratified analysis of the relationship between hemoglobin and ferritin and the risk of GDM
| Stratified analysis for hemoglobin studies | ||||||
|---|---|---|---|---|---|---|
| Subgroup | Studies (n) | OR (95% CI) | Heterogeneity | Multivariate meta‐regression | Univariate meta‐regression | |
| P‐value | I2 (%) | P‐value | P‐value | |||
| Geographic area | ||||||
| Eastern | 6 | 1.64 (1.29–2.07) | 0.119 | 42.9% | 0.898 | 0.254 |
| Western | 3 | 1.13 (0.70–1.82) | 0.500 | 0.0% | ||
| Design | ||||||
| Longitudinal | 7 | 1.71 (1.33–2.21) | 0.199 | 30.0% | 0.833 | 0.303 |
| Cross‐sectional | 2 | 1.17 (0.79–1.71) | 0.384 | 0.0% | ||
| Collecting hemoglobin | ||||||
| 1° Trimester | 3 | 1.58 (1.07–2.35) | 0.634 | 0.0% | ||
| 2° Trimester | 2 | 1.11 (0.67–1.84) | 0.321 | 0.0% | 0.904 | 0.220 |
| 3° Trimester | 3 | 1.40 (0.99–1.98) | 0.067 | 63.0% | ||
| Mixed (50.3% 1st trimester) | 1 | 2.42 (1.43–4.10) | — | — | ||
| GDM ascertainment | ||||||
| Carpenter‐Coustan | 5 | 1.45 (1.02–2.04) | 0.207 | 32.2% | 0.847 | 0.077 |
| WHO | 2 | 2.01 (1.41–2.86) | 0.352 | 0.0% | ||
| IADPSG | 2 | 1.12 (0.74–1.69) | 0.424 | 0.0% | ||
| Anemia | ||||||
| Anemic women included | 6 | 1.36 (1.06–1.75) | 0.172 | 35.3% | 0.820 | 0.198 |
| Anemic women excluded | 3 | 2.02 (1.36–3.00) | 0.476 | 0.0% | ||
| Adjusted for age and BMI | ||||||
| Adjusted | 6 | 1.54 (1.15–2.06) | 0.268 | 22.0% | 0.824 | 0.907 |
| Unadjusted | 3 | 1.50 (1.10–2.05) | 0.061 | 64.2% | ||
| Adjusted for CRP | ||||||
| Adjusted | 1 | 3.05 (1.39–6.69) | ‐ | ‐ | 0.699 | 0.157 |
| Unadjusted | 8 | 1.44 (1.16–1.80) | 0.270 | 20.1% | ||
| Age | ||||||
| <30 years | 7 | 1.43 (1.14–1.79) | 0.194 | 30.7% | 0.385 | 0.229 |
| ≥30 years | 2 | 2.35 (1.30–4.24) | 0.322 | 0.0% | ||
| Study quality | ||||||
| <75% | 1 | 2.42 (1.43–4.10) | ‐ | ‐ | 0.824 | 0.166 |
| ≥75% | 8 | 1.39 (1.11–1.76) | 0.294 | 17.3% | ||
| Stratified analysis for ferritin studies | ||||||
| Geographic area | ||||||
| Eastern | 5 | 2.15 (1.27–3.64) | 0.212 | 31.3% | 0.931 | 0.912 |
| Western | 2 | 2.05 (1.29–3.25) | 0.655 | 0.0% | ||
| Design | ||||||
| Longitudinal | 4 | 2.15 (1.44–3.21) | 0.802 | 0.0% | 0.814 | 0.806 |
| Cross‐sectional | 3 | 1.92 (0.96–3.85) | 0.083 | 59.7% | ||
| Collecting ferritin | ||||||
| 1° Trimester | 2 | 2.13 (1.17–3.89) | 0.576 | 0.0% | 0.697 | 0.897 |
| 2° Trimester | 1 | 1.84 (0.95–3.57) | ‐ | ‐ | ||
| 3° Trimester | 4 | 2.25 (1.30–3.91) | 0.138 | 45.6% | ||
| GDM ascertainment | ||||||
| Carpenter‐Coustan | 2 | 2.17 (1.27–3.71) | 0.410 | 0.0% | 0.771 | 0.959 |
| WHO | 4 | 1.83 (0.96–3.49) | 0.164 | 41.3% | ||
| Undefined (clinician) | 1 | 2.27 (1.20–4.30) | — | — | ||
| Anemia | ||||||
| Anemic women included | 5 | 2.01 (1.37–2.95) | 0.286 | 23.0% | 0.814 | 0.677 |
| Anemic women excluded | 2 | 2.50 (1.12–5.58) | 0.430 | 0.0% | ||
| Adjusted for age and BMI | ||||||
| Adjusted | 6 | 2.02 (1.34–3.06) | 0.311 | 16.0% | 0.771 | 0.796 |
| Unadjusted | 1 | 2.27 (1.20–4.30) | — | — | ||
| Adjusted for CRP | ||||||
| Adjusted | 2 | 2.48 (1.47–4.18) | 0.643 | 0.0% | 0.814 | 0.450 |
| Unadjusted | 5 | 1.83 (1.15–2.91) | 0.276 | 21.7% | ||
| Age | ||||||
| <30 years | 5 | 1.83 (1.15–2.91) | 0.276 | 21.7% | 0.814 | 0.450 |
| ≥30 years | 2 | 2.48 (1.47–4.18) | 0.643 | 0.0% | ||
| Ferritin determination | ||||||
| IRMA | 2 | 2.17 (1.27–3.71) | 0.410 | 0.0% | 0.931 | 0.773 |
| ELISA | 4 | 2.10 (1.31–3.7) | 0.165 | 41.1% | ||
| Chemiluminescence | 1 | 1.33 (0.23–7.71) | — | — | ||
BMI = body mass index; CRP = C‐reactive protein; ELISA = Enzyme‐Linked ImmunoSorbent Assay; IADPSG = International Association of Diabetes and Pregnancy Study Groups; IRMA = ImmunoRadioMetric Assay; WHO = World Health Organization.
[Correction added on 27 December 2016, after first online publication: The presentation of P‐values under Multivariate meta‐regression and Univariate meta‐regression columns was previously wrong and has been corrected in this current version.]