PROTECT: PRegnancy Outcomes using continuous glucose monitoring TEChnology in pregnant women with early-onset Type 2 diabetes: a multicentre randomised controlled trial – study protocol

Early-onset type 2 diabetes (EOT2D), meaning type 2 diabetes diagnosed before the age of 40 disproportionately affects women from socially deprived and minority ethnic groups. EOT2D is now the most common form of pre-existing diabetes complicating pregnancy. These pregnancies carry high risks of congenital anomalies, stillbirth, neonatal death, and of both maternal and neonatal morbidity. Maternal glycaemia is the key modifiable risk factor yet remains suboptimal and is often accompanied by limited self-monitoring of blood glucose (SMBG). Continuous Glucose Monitoring (CGM) offers continuous real-time glucose profiles, potentially enabling better dietary, lifestyle and therapy adjustments. The PROTECT trial is a multicentre, randomised controlled trial designed to evaluate whether CGM improves maternal glucose and neonatal outcomes in women with EOT2D. The trial will recruit 422 pregnant participants (≤ 16 weeks 0 days’ gestation, HbA1c ≥ 43 mmol/mol) from around 20 UK NHS antenatal diabetes clinics. After a run-in phase with masked CGM, participants will be randomised to either real-time CGM (FreeStyle Libre 3) or standard SMBG. The primary maternal outcome is percentage of time in pregnancy-specific glucose target range (3.5–7.8 mmol/L). The primary neonatal outcome is a composite of neonatal care unit admission or death. Secondary outcomes include maternal HbA1c, glycaemic variability, insulin use, obstetric complications, neonatal morbidity, psychosocial measures, and cost-effectiveness. An internal pilot will assess recruitment feasibility, before proceeding to the full trial. Qualitative interviews with women and healthcare professionals will explore barriers and facilitators to CGM use. Statistical analyses will follow intention-to-treat principles. This is the largest trial to date investigating CGM in EOT2D pregnancy, aiming to generate robust evidence on clinical efficacy, lived experiences, and economic impact, informing future NHS policy and practice. ISRCTN12804317 Registration Date: 23/10/2023.