GCK and gestational diabetes: However, when we limit our association analysis to include only females with pregnancy phenotypes in their medical records, we see the PPV for gestational diabetes rise to 1.0 for HNP and 0.75 for UKB (respectively, 0 of 2,363 and 2 of 10,555 pregnant females without gestational diabetes were heterozygous for qualifying GCK variants), suggesting this may indeed be a genetic condition worthy of prepregnancy population screening.