Iron Status and Gestational Diabetes

Summary

A meta-analysis 3 evaluating the association between ferritin status and gestational diabetes (GDM) included 10 observational studies with a total of 4 690 subjects. The summary relative risk comparing persons with the highest concentration categories of ferritin with the lowest concentration categories of ferritin was 1.87 (95% CI1.50 to 2.34; I² = 20%). Linear dose-response showed that an increase in ferritin of 10 μg/L increased the risk of GDM by 8% (1.08, 95% CI 1.05 to 1.13, I²= 55%).

Another meta-analysis 2 investigated the association of iron biomarkers and dietary iron exposure with GDM. 33 studies (n=44 110) published in 2001-2017 were included. The standardized mean differences (SMD) in women who had GDM compared to pregnant women without were 0.25 µg/dL (95% CI 0.001 to 0.50) for iron, 1.54 ng/mL (0.56 to 2.53) for ferritin, 1.05% (0.02 to 2.08) for transferrin saturation, and 0.81 g/dL (0.40 to 1.22) for hemoglobin. Adjusted odds ratio for GDM were 1.58 (95% CI 1.20 to 2.08) for ferritin, 1.30 (1.01 to 1.67) for hemoglobin, and 1.48 (1.29 to 1.69) for dietary heme intake.

A case-control study 1 4 of 350 GDM cases and 349 non-GDM controls was conducted in participants from the Danish National Birth Cohort. Blood was collected at a mean ± SD gestational age of 9.4 ± 3.2 wk. Plasma biomarkers of iron stores, including ferritin and soluble transferrin receptor (sTfR), were measured. Logistic regression was used to estimate the OR of GDM associated with quintiles of plasma biomarkers of body iron stores, controlling for maternal age, family history of diabetes, exercise in pregnancy, parity, and prepregnancy body mass index (BMI). Plasma concentrations of both ferritin and sTfR in early pregnancy were significantly higher in GDM cases than in controls [means ± SDs: 80.6 ± 56.0 compared with 71.8 ± 50.1 μg/L (P = 0.03) and 1.5 ± 0.7 compared with 1.4 ± 0.6 mg/L (P = 0.002) for ferritin and sTfR, respectively]. Ferritin was positively and significantly associated with GDM risk even after adjustment for major risk factors of GDM, including prepregnancy BMI. ORs across increasing quintiles of ferritin were 1.00 (reference), 1.25 (95% CI 0.70 to 2.22), 1.89 (95% CI 1.06 to 3.37), 0.82 (95% CI 0.46 to 1.48), and 2.34 (95% CI 1.30 to 4.21) (P-linear trend = 0.02).