RBP4 and gestational diabetes: In a study on circulating retinol-binding protein 4 (RBP4) levels in GDM patients, a meta-analysis showed that circulating RBP4 levels in Asian women with GDM in the second and third trimesters of pregnancy were significantly higher than those in normal controls, suggesting that RBP4 may be involved in the metabolic abnormalities of GDM (59).