Inclusion Criteria:  confirmed diagnosis of type one diabetes duration of the disease for minimum of one year before inclusion in the study multiple daily insulin injection therapy or insulin pump glycemia monitoring with continuous glucose monitoring systems (FreeStyle Libre Flash Glucose Monitoring System, Abott) for a minimum of 3 months before inclusion in the study glucose data availability from the sensor > 80% for a determined period of monitoring patient age > 18 years and < 40 years available medical records from the preconception period (3 months before conception) first trimester of pregnancy body mass index < 25kg/m2 glycated haemoglobin < 7.0% signed informed consent  Exclusion Criteria:  other types of diabetes except type one: type 2 diabetes, diabetes developed during pregnancy, diabetes as a result of genetic defect of beta-cells of the pancreas using other therapy besides insulin in treating diabetes changes to the specific insulin therapy in preconception period or during pregnancy; defined as switching from multiple daily insulin injection therapy to insulin pumps and vice versa patient's inability for regular hospital visits (defined as once monthly during pregnancy) patients unable to understand the protocol and the goal of the study patients unable to read and write multiple pregnancy glycated haemoglobin > 7.0% in all pregnancy trimesters significant weight gain during pregnancy (>20 kilograms) glucose data availability from the sensor < 80% unavailability of preconception medical records unavailability of medical records from pregnancy and pregnancy outcomes