Maternal Adiposity and Inflammation: Risk Factors for Iron Deficiency in Pregnancy

Obesity and iron deficiency (ID) are global health concerns in pregnancy, with serious consequences for mother and offspring. The inflammatory state associated with obesity and its potential contribution to ID/anemia is unclear.

This study aims to investigate the associations among maternal adiposity, the mediating role of inflammation, and iron status. We also aim to examine how adiposity affects the predictive accuracy of early pregnancy iron markers for late pregnancy ID risk.

This secondary analysis of a double-blind randomized controlled trial included singleton pregnancies supplemented with a multivitamin containing 17 mg/d of iron. Body mass index (BMI), body composition [12 gestational weeks (GW)], iron markers (12, 28, 36 GW), and hemoglobin/hematological indices (12, 28 GW, postpartum) were assessed. Proinflammatory cytokines were used to calculate an inflammation score and categorized as high/low inflammation.

A total of 125 pregnant women were included: 43 normal weight, 44 overweight, and 38 with obesity. At 36 GW, ID was present in 50% of women with obesity, 40.9% of those overweight, and 30.2% with normal BMI. High BMI and fat mass index (FMI) at 12 GW predicted lower ferritin at 36 GW (BMI β = -0.253, P = 0.020; FMI β = -0.265, P = 0.010), and all adiposity measures predicted higher soluble transferrin receptor (sTfR). Transferrin saturation was lower in women with obesity at 12 and 28 GW (12 GW 23.9%, 24.5%, 30.3%, P = 0.016; 28 GW 13.2%, 17.7%, 17.2% P < 0.001, obesity, overweight, and normal weight, respectively). At 36 GW, pregnant women with obesity and higher inflammation score had lower ferritin than normal weight women (15.0 compared with 20.3 μg/L, P = 0.041). sTfR at 12 GW was the best predictor of ID at 36 GW [area under curve (AUC) = 0.738, P < 0.001], especially in overweight/obesity (AUC = 0.744, P < 0.001).

High adiposity, mediated by inflammation, increases the risk of ID in the late third trimester. sTfR in early pregnancy emerges as an effective marker for predicting ID in late pregnancy.