INTRODUCTION: The placenta plays a pivotal role in supporting fetal growth and disruptions in its development and function can impact fetal outcomes. While placental pathology has been extensively studied in clinical conditions such as pre-eclampsia and fetal growth restriction (FGR), the association between placental abnormalities and gestational diabetes mellitus (GDM) is still unclear. This study aims to explore the placental pathology associated with GDM, shedding light on potential links to adverse perinatal outcomes. METHODS: A retrospective cohort study was conducted using electronic patient data from the Fetal Medicine and Neonatal Units at University College London Hospital. Placental samples were obtained and analysed at Great Ormond Street Hospital. Maternal demographics, obstetric history and placental histopathology were reviewed. Statistical analyses were performed to identify associations and risk factors. RESULTS: Of the 2580 pregnancies analysed, 341 were GDM pregnancies, 549 had FGR and 66 had both GDM and FGR. GDM pregnancies required increased rates of obstetric intervention and neonatal care admission. Placental pathology in GDM revealed a higher prevalence of maternal vascular malperfusion (MVM) lesions, whilst GDM-related FGR showed further associations with MVM lesions and adverse perinatal outcomes. DISCUSSION: Our study highlights MVM lesions as a prominent feature in the placentas of GDM pregnancies, especially when associated with FGR. These lesions are linked to adverse perinatal outcomes, emphasizing the need for enhanced antenatal care in these cases. The study contributes insights into the complex relationship between GDM, placental pathology and adverse fetal outcomes, laying the foundation for future investigations into early interventional strategies.