Table 3. Assessment across the statistically significant associations for gestational diabetes.
| Level of evidence | Criteria used | Decreased risk | Increased risk |
|---|---|---|---|
| Convincing | >1000 cases, a P<10−6, not large heterogeneity (I2 <50%), 95% prediction interval excluding the null value, no evidence for small-study effects b and excess significance bias c | Low vs. Normal BMI (cohort) | BMI ~30–35 vs. Normal weight, BMI >35 vs. Normal weight, Hypothyroidism (all) |
| Highly suggestive | >1000 cases, a P<10−6 and nominally statistically significant effect present at the largest study | Pre-pregnancy BMI (as a continuous variable), Overweight vs. Normal BMI (cohort), BMI >30 vs. normal weight, Overweight vs. Non-overweight women (cohort), Overweight vs. Non-overweight (case-control), Obese vs. non-obese women (cohort), Snoring, Sleep-disordered breathing, Polycystic ovary syndrome, Family history of diabetes |
|
| Suggestive | >1000 cases, a P<10−3 | Low vs. Normal BMI (case-control), Serum 25(OH)D level | Hemoglobin concentration (g/dL), Mean platelet volume, Insufficient vitamin D, Dietary total iron intake, Subclinical hypothyroidism, Extreme sleep duration, Age at menarche |
| Weak | The rest associations with a P < 0.05 | Maternal iron deficiency, DQ6, Selenium level, Prenatal exercise + co-interventions, Prenatal exercise (cohort studies), Prenatal exercise (cross-sectional studies) | Chemerin levels, Ferritin concentration (ng/mL), Betatrophin levels, Ferritin (highest vs lowest ferritin levels) (cohorts), Serum ferritin (GMT-women vs non-GMD), Hemoglobin levels, Ferritin (highest vs lowest ferritin levels) (mixed), Serum retinol-binding protein-4, DQ2, DR13, DR17, Thyroid antibodies (case-control), Thyroid antibodies (All studies), 25(OH)D5 <50 nmol/l, 25(OH)D <75 nmol/l, Overweight vs. Normal BMI (case-control), Obese vs. non-obese women (case-control), Obstructive sleep apnea, Overt hypothyroidism, Periodontitis, Isolated Single Umbilical Artery |
Abbreviations: BMI, Body Mass Index; GDM, gestational diabetes mellitus.
a P indicates the P-values of the meta-analysis random effects model.
b Small study effect is based on the P-value from the Egger’s regression asymmetry test (P<0.10).
c Based on the P-value (P<0.05) of the excess significance test using the largest study (smallest standard error) in a meta-analysis as the plausible effect size.