GDM
Seven studies reported GDM as an outcome34,35,43,44,47,54,55. When results were pooled, pregnant women in the top tertile of diet quality scores had a lower risk of GDM compared with those in the bottom tertile (OR: 0.77; 95 CI: 0.65, 0.90; I2 = 72%; P-heterogeneity <0.01; Figure 3). The results were consistent when the moderate-quality study34 was excluded (Table S6). Subgroup analysis suggested that the association is stronger in studies with adjustment for education level (n=4, OR: 0.64; 95 CI: 0.56, 0.73; I2 =0) than in those without adjustment for education level (n=3, OR: 0.91; 95 CI: 0.83, 0.99; I2 =0). No heterogeneity between studies in each subgroup requiring further exploration was identified (Table S7).