['To assess whether the common rs8111699 (C528G) variant in STK11 is related to metabolic risk markers in pregnant women and to gestational diabetes mellitus (GDM).', 'Cross-sectional study.', 'Hospital.', 'A total of 561 pregnant women: 318 without and 243 with GDM (National Diabetes Data Group criteria).', 'None.', "rs8111699 variant in STK11 (Taqman technology). Fasting glucose, insulin (homeostatic model assessment of insulin resistance and β-cell function [HOMA-IR and -β]) and C-peptide assessed at 24-28 weeks' gestation.", 'In non-GDM women, the G allele in rs8111699 was associated with lower HOMA-IR (CC: 1.3 ± 0.1 mIU/L; GG: 0.9 ± 0.1 mIU/L) and HOMA-β (CC: 165 ± 20 mIU/L; GG: 118 ± 10 mIU/L). In GDM women, the G allele was related to lower body mass index (BMI; CC: 27.9 ± 1.0 kg/m(2); GG: 24.5 ± 0.6 kg/m(2)) and C-peptide (CC: 2.3 ± 0.1 ng/mL; GG: 1.6 ± 0.1 ng/mL). The GG genotype was less frequently observed in GDM women (18% vs. 26%), particularly in heavier GDM women (BMI > median: 14% vs. 28%).'] Is a common gene variant in STK11 associated with metabolic risk markers and diabetes during gestation?