Effect of Dietary Patterns on Maternal Body Composition and Bone Mineral Density During Three Trimesters in Chinese Pregnant Women: A Cross-Sectional Study

<b>Background/Objectives</b>: This study aims to assess dietary quality among Chinese pregnant women across three gestational trimesters using different assessment indices while investigating the relationship between dietary patterns and longitudinal alterations in maternal body composition parameters and bone mineral density (BMD) during pregnancy. <b>Methods</b>: A total of 556 healthy pregnant women were recruited. Dietary intake was assessed utilizing a semi-quantitative food frequency questionnaire (FFQ). Diet quality was evaluated through three indices: the Dietary Balance Index for Pregnant Women (DBI-P), the Dietary Inflammatory Index (DII), and the Eastern Health Diet Index (EHDI). Multiple linear regression models and mediation analyses were constructed to elucidate the relationships between dietary indices, body composition parameters, and BMD. <b>Results</b>: In the first trimester, excessive dietary intake was associated with increased maternal fat mass but reduced BMD, while insufficient intake correlated with declines in muscle mass, water compartments, and inorganic salt levels. Pro-inflammatory diets further exacerbated reductions in non-fat body composition, including protein and muscle mass. By the second trimester, low-quality diets continued to negatively affect muscle mass and water balance, whereas no significant dietary effects on body composition or BMD were observed in the third trimester. Mediation analyses revealed that body composition partially mediated the relationship between dietary imbalance and reduced BMD. <b>Conclusions</b>: Unbalanced, pro-inflammatory, and low-quality diets during early-to-mid pregnancy contribute to adverse changes in maternal body composition and bone health, especially in the first and second trimesters, with the DBI-P index demonstrating superior applicability for assessing dietary impacts in Chinese pregnant women.