BACKGROUND : Gestational diabetes mellitus (GDM) is correlated with an increased risk of adverse perinatal outcomes for both the mother and offspring. Previous research has reported correlations between maternal dietary patterns and GDM, but such evidence for twin pregnancies is lacking. This study aimed to identify maternal dietary patterns in the second trimester and investigate their relationships with the risk of GDM among women who were pregnant with twins in China. METHODS : A longitudinal twin pregnancies birth cohort study of women who were pregnant with twins in China was conducted. Maternal dietary intake in the second trimester was recorded by using a food frequency questionnaire prior to the diagnosis of GDM among participants from the prospective twin pregnancies birth cohort in Chongqing City. GDM was diagnosed with a 75 g 2-h oral glucose tolerance test at 23-26 weeks of gestation. Dietary patterns were identified by principal components analysis, and the correlations between dietary pattern and GDM were examined using multivariable logistic regression analyses. RESULTS : Of the 324 participants, 101 (31.2%) were diagnosed with GDM. Four dietary patterns were identified: a vegetable-based pattern, a poultry-and-fruit-based pattern, a sweet-based pattern and a plant-protein-based pattern. Multivariate analysis showed that none of the dietary patterns were correlated with the risk of GDM among women who were pregnant with twins, but the sweet-based dietary pattern, which was associated with a higher GDM risk for quartile 4 versus quartile 1 (OR 2.69; 95% CI: 1.09, 6.66) among non-overweight women (prepregnancy BMI < 24.0). CONCLUSIONS : Dietary patterns were not correlated with later GDM risk among women who were pregnant with twins in western China, whereas a high intake of sweets was associated with a higher risk for GDM among women who were not overweight prior to pregnancy. BACKGROUND : ChiCTR-OOC-16008203. Retrospectively registered on 1 April 2016.