Objectives: To compare peri-partal parameters between two groups of pregnant women – with and without gestational diabetes mellitus (GDM), to correlate degree of glucose abnormality with incidence of peri-partal morbidity and, finally, to analyse the potential effect of comorbidities (i.e. obesity, hypertension, thyreopathy, polycystic ovary syndrome, trombophylia, anemia, allergy, smoking) on pregnancy outcomes. Design: Epidemiological observational „case-control“ study. Methods: The study comprised 432 pregnant women (364 with GDM diagnosis, 68 healthy controls) followed during a period 2011-2013. GDM was diagnosed by oral glucose tolerance test in 24-28th week of gestation (by fasting plasma glucose >5,6 mmol/l or >8,8 mmol/l in 60th min or >7,8 mmol/l in 120th min post-75g glucose load). Following peri-partal parameters were studied: ultrasonographic examination before delivery, a date of delivery, length of childbirth, induction, perinatal complications, post-delivery complications, section, abnormity in pH, base excess, Apgar score, birth weight. Results: Subjects with GDM had significantly increased rate of labour induction compared to healthy controls (P=0.0035, chi-square test). Subgroup of GDM women classified as having a higher risk for adverse perinatal outcomes by a definition of Czech Obstetric and Gynaecology Society had significantly more labour inductions, more sections and instrumental deliveries. New-borns of those mothers had significantly more common worse perinatal outcomes (Apgar score and macrosomia). Conclusion: Based on our data risk stratification of GDM subjects according to Czech Obstetric and Gynaecology Society appears relevant and justified.