Type I diabetes mellitus (T1DM) affects about 0.1-0.2% of all pregnancies. T1DM in pregnancy increases the risk of maternal and neonatal complications.

Continuous glucose monitoring systems (CGM) provide a continuous display of measured glucose. Studies have shown improved pregnancy outcomes for patients with T1DM using CGM when compared to capillary blood glucose measurements.

This prospective observational study analyses impact of glycemic variability on development of large-for-gestational-age neonates and effects of hypoglycemia during pregnancy on pregnancy outcomes.

Furthermore, overall glycemic regulation, different insulin metrics and C-peptide concentration during pregnancy will also be assesed.

Up to 200 patients with type one diabetes will be enrolled in the study during first trimester of pregnancy. Medical history, clinical examination, anthropometric measurements and laboratory work-up will be obtained at first visit. Glucose metrics are provided from continuous glucose monitoring systems and blood glucose measurements .

Following the initial evaluation, patients will be regularly examined in the hospital setting once a month during pregnancy. Following evaluations will include the same procedures as the first one.

Pregnancy outcomes that will be analysed: spontaneous abortion, preterm birth, large-for-gestational-age neonates, macrosomia, small-for-gestational-age neonates, birth weight, congenital anomalies, APGAR score, neonatal hypoglycemia, intensive care unit admission for mother and/or infant.

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

Patients enrolled in the study are women who are patients of the Clinic for gynecology and obstetrics and who match the inclusion criteria.