Prepregnancy Body Mass Index is Positively Associated with Dietary Inflammatory Index and C‐Reactive Protein Concentrations during Pregnancy.
Authors: Shin Dayeon , Lee Kyung Won , Hur Junguk , Chung Hae‐Kyung , Shivappa Nitin , Wirth Michael D. , Hébert James R. 
Published: November 2023

ObjectivePregnancy overweight and obesity have been associated with adverse pregnancy outcomes, but the underlying mechanisms through inflammation are unclear. Considering that both prepregnancy body mass index (BMI) and inflammation are closely associated with dietary factors, it is important to understand how prepregnancy BMI is associated with diet‐induced inflammation during pregnancy. There have been limited research on how prepregnancy body mass index (BMI) is associated with inflammation during pregnancy. The present study aimed to examine the association between prepregnancy BMI and Dietary Inflammatory Index (DII)TM and C‐reactive protein (CRP) concentrations during pregnancy.Research Design and MethodsThe study included 631 U.S. pregnant women from the National Health and Nutrition Examination Survey, 2003–2012. Prepregnancy BMI was calculated based on self‐reported prepregnancy weight and measured height. The cut‐points of <18.5 (underweight), 18.5–24.9 (normal), 25.0–29.9 (overweight), and ≥30 kg/m2 (obese) were used to categorize pregnant women's weight status before pregnancy. The DII, a literature‐driven dietary index to assess the inflammatory properties of diet, was estimated based on one‐day 24‐hour recall. CRP was measured by latex‐enhanced nephelometry by a Behring Nephelometer for quantitative CRP determination. Multivariable logistic regression analysis was performed to estimate adjusted odds ratios (AORs) and 95% confidence intervals (95% CIs) on the association of prepregnancy BMI categories with the DII and CRP concentrations during pregnancy.ResultsCategories of prepregnancy BMI significantly differed by the tertiles of the DII (P=0.0068). A higher prevalence of normal weight women (44.4%) were in the tertile 1 of the DII (anti‐inflammatory group), whereas higher percentage of women with overweight and obese prepregnancy BMI (67.9%) were in the tertile 3 of the DII (pro‐inflammatory group). After controlling for race/ethnicity, family poverty income ratio, education, marital status, month in pregnancy, and smoking status during pregnancy, women with obesity before pregnancy had an increased risk for being in the highest tertile of the DII and CRP concentrations compared to women with normal weight (AORs 2.51, 95% CIs 1.05–5.97; AORs 35.26, 95% CIs 8.53–145.50, respectively). The partial correlation of prepregnancy BMI with the DII and CRP concentration was 0.09 (P<0.05) and 0.40 (P<0.001), respectively, controlling for age, race/ethnicity, education level, family poverty income ratio, marital status, and smoking status during pregnancy.ConclusionsThe findings suggest that prepregnancy BMI is statistically significantly and positively associated with DII values and CRP concentrations during pregnancy in U.S. representative pregnant women. Nutrition education may be warranted for reproductive aged women with obesity to reduce inflammation through diet that may, in turn, eventually reduce adverse pregnancy outcomes.