Pre‐pregnancy body mass index is associated with dietary inflammatory index and C‐reactive protein concentrations during pregnancy

There have been a limited number of studies examining the association between prepregnancy body mass index (BMI) and dietary inflammation during pregnancy. Our aim is to examine the association between pre‐pregnancy BMI and the Dietary Inflammatory Index (DII)™ and C‐reactive protein (CRP) concentrations during pregnancy. The study included 631 pregnant American women from the National Health and Nutrition Examination Survey (NHANES) crosssectional examinations from 2003 to 2012. Pre‐pregnancy BMI was calculated based on self‐reported pre‐pregnancy weight and measured height. The cut‐offs of <18.5 (underweight), 18.5–24.9 (normal), 25.0–29.9 (overweight), and ≥30 kg/m² (obese) were used to categorize the weight status of pregnant women prior to pregnancy. The DII, a literature‐based dietary index to assess the inflammatory properties of diet, was estimated based on a one‐day 24‐h recall. Multivariable linear and logistic regressions were performed to estimate beta coefficients and the adjusted odds ratios (AORs) and 95% confidence intervals (95% CIs) on the association of pre‐pregnancy BMI categories with the DII and CRP concentrations during pregnancy. After controlling for variables including: race/ethnicity, family poverty income ratio, education, marital status, month in pregnancy, and smoking status during pregnancy; women who were obese before pregnancy (n = 136) had increased odds for being in the highest tertile of the DII and CRP concentrations compared to women with normal weight (AORs 2.40, 95% CIs 1.01–5.71; AORs 24.84, 95% CIs 6.19–99.67, respectively). These findings suggest that women with pre‐pregnancy obesity had greater odds of reporting higher DII and having elevated CRP. In conclusion, high pre‐pregnancy BMI was associated with increased odds of pro‐inflammatory diet and elevated CRP levels during pregnancy in the USA.