['To examine the association between uric acid (UA) level during the first 20 weeks of pregnancy and the development of gestational diabetes mellitus (GDM) and preeclampsia in the second half of pregnancy.', 'The study population included registered births (n = 5507) between 2001 and 2007 in a tertiary medical center. The UA levels during the first 20 weeks of pregnancy were sorted by UA ≤ 2.4 mEq/L; UA = 2.5-4.0 mEq/L, UA = 4.1-5.5 mEq/L, and UA > 5.5 mEq/L. The linear-by-linear chi-square test and ROC curves were used to determine the association between UA level during the first 20 weeks and pregnancy complications. Multivariate analyses were performed to demonstrate whether UA level is an independent factor for the prevalence of preeclampsia and GDM.', 'Significant linear association was documented between UA level in the first 20 weeks and the prevalence of GDM and mild preeclampsia. The lowest and the highest prevalence of GDM were found in the UA ≤ 2.4 mEq/L group (6.3%) and in the UA > 5.5 mEq/L group (10.5%) (p < 0.001), respectively. Mild preeclampsia was diagnosed in 2.1% of the patients from the UA ≤ 2.4 mEq/L group, 3.3% from the UA = 2.5-4.0 mEq/L group, 5.3% from the UA = 4.1-5.5 mEq/L group, and 4.5% from the UA > 5.5 mEq/L group (p < 0.001). Three multiple logistic regression models controlling for maternal age showed that UA level is an independent risk factor for both GDM and mild preeclampsia.'] Is high uric acid level during the first 20 weeks of pregnancy associated with higher risk for gestational diabetes mellitus and mild preeclampsia?