FreeStyle Libre in Pregnancy Study

Inclusion Criteria: * Age ≥ 18 years * Type 1, type 2 or Gestational Diabetes Mellitus (GDM) (confirmed diagnosis via Oral Glucose Tolerance Test (OGTT)) * Currently testing Blood Glucose(BG), on average at least 2 times per day * Participant is ≥12+0 weeks gestation with a singleton pregnancy * In the investigator's opinion, technically capable of using device Exclusion Criteria: * Concomitant disease or condition that may compromise patient safety including and not limited to; cardiac disease or event, sickle cell disease, cystic fibrosis, severe mental illness, known or suspected eating disorder or any uncontrolled long term medical condition * Currently receiving dialysis treatment or planning to receive dialysis during the study or, moderate to advanced nephropathy (serum creatinine ≥120 micromol/litre or total protein excretion exceeds 2 g/day or urinary albumin:creatinine ratio \>30 mg/mmol, estimated glomerular filtration rate (eGFR) may not be used) * Diabetic Ketoacidosis (DKA) (in the previous 6 months) * Known (or suspected) allergy to medical grade adhesives * In the investigator's opinion the participant is unsuitable to participate due to any other cause/reason, considering guidelines (e.g. National Institute for Health and Care Excellence (NICE) and International Diabetes Federation(IDF)) for Diabetes in Pregnancy for HbA1c and Blood Pressure * Experiencing any of the following conditions for current pregnancy: * Pre-eclampsia * HELLP syndrome (haemolysis, elevated liver enzymes and low platelet count) * Prescribed Tocolytic drugs for treatment of preterm labour