Overweight and obesity in early pregnancy are associated with poorer maternal iron status and inhibited placental iron transfer

Introduction: Women in countries undergoing the nutrition transition increasingly face a “double burden” of malnutrition. Concurrent iron deficiency (ID) and overweight during pregnancy is of particular concern given the potential adverse effects on fetal growth and infant development.

Objectives: To determine the association of 1) pre-pregnant maternal adiposity with maternal iron status and inflammation in early pregnancy, and 2) maternal adiposity and fetal iron status.

Methods: We examined longitudinal data from a prospective cohort of 1,611 pregnant mothers in China. Women were enrolled in early pregnancy and followed through parturition. Venous blood samples were obtained at enrollment, in the third trimester, and at birth and analyzed for a range of hematological and iron biomarkers.

Results: We observed a negative relationship between maternal body mass index (BMI) and iron status in early pregnancy (soluble transferrin receptor (sTfR): r = 0.19, P<0.001; erythrocyte zinc protoporphyrin: r = 0.07; P=0.02). Maternal BMI was positively associated with inflammation in early pregnancy (C-reactive protein: r = 0.30; P<0.001). In multiple linear regression models adjusting for maternal iron status and inflammation in late pregnancy, maternal BMI was negatively associated with cord blood iron status using both serum ferritin and sTfR as biomarkers of iron status (P<0.001 and P=0.015, respectively).

Conclusions: Concurrent overweight and ID during pregnancy may inhibit placental transfer of iron to the fetus through inflammatory pathways. Rising rates of overweight among women in nutrition transition countries may undercut efforts to mitigate ID during pregnancy and prevent its adverse consequences.