Publication:

Association of serum ferritin concentration in early pregnancy with the risk of subsequent development of gestational diabetes mellitus

Background Gestational diabetes mellitus (GDM) is among the commonest medical complications of pregnancy and South Asian women are affected at lower body mass indices than Western populations. Serum ferritin reflects body iron stores and is also an acute-phase reactant; iron-catalysed oxidative stress may impair insulin action. We examined whether early-pregnancy ferritin predicts subsequent GDM.

Methods In this prospective observational study, 111 antenatal women at 12–18 weeks were enrolled consecutively at a tertiary teaching hospital. Fasting serum ferritin was measured by chemiluminescent microparticle immunoassay. Women were followed to 24–28 weeks, when GDM was diagnosed by 75g oral glucose testing using American Diabetes Association criteria. Analysis used Mann–Whitney U and chi-square tests, Spearman correlation, multivariable logistic regression and receiver operating characteristic (ROC) analysis.

Results GDM developed in 24/111 women (21.6%). Median ferritin was higher in the GDM group (55.35 vs 24.00 ng/mL; p<0.0001). GDM prevalence rose across ferritin quintiles from 8.7% to 77.3% (p<0.0001). Ferritin correlated with glucose challenge values (ρ=0.576; p<0.0001) and independently predicted GDM after adjustment for age, BMI, gravida and haemoglobin (adjusted odds ratio 2.41 per 10 ng/mL; 95% CI 1.68–3.44). Area under the ROC curve was 0.865; a cut-off of 39.9 ng/mL gave 79.2% sensitivity, 92.0% specificity and 94.1% negative predictive value.

Conclusions Elevated early-pregnancy serum ferritin is independently and gradedly associated with subsequent GDM and discriminates well between affected and unaffected women. Ferritin is inexpensive and already widely measured antenatally and may permit risk stratification well before conventional screening; multicentre validation is required.