The research presented involves three inter-related studies involving the care of patients with gestational diabetes mellitus (GDM), who were either inpatients at the A1 Ain Hospital or who attended outpatient clinics at the A1 Ain Medical District, United Arab Emirates (UAE). The main study (prospective randomised controlled trial) examined the impact of pharmaceutical care provision to patients with GDM; intervention patients (n=99) received a structured pharmaceutical care service while control patients (n=66) received traditional services. Over the study period (18 months), the intervention group patients showed significant (p < 0.05) improvements (as indicated by HbA_1c values) in a range of outcome measures including diabetes knowledge, health-related quality of life, maternal and neonatal complications when compared with the control group patients. The second study delineated (using logistic regression modelling) factors implicated in putting GDM patients at risk of developing early postpartum diabetes mellitus. Within the population studied (n-165), risk factors were: severe hyperglycaemia (OR 4.62), family history of diabetes mellitus (OR 5.51), gravida >5 (OR 3.23) and gestational age at GDM diagnosis < 16 weeks (OR 3.96). In the third study, a comparative correlation was conducted between the values of oral glucose tolerance tests (OGTTs) and pregnancy outcomes based on two different standard procedures for interpreting the OGTT results. The study indicated that using criteria for diagnosis of GDM based on the National Diabetes Data Group would have failed to diagnose 12.1% of patients who were diagnosed using the Coustan and Carpenter criteria and treated for their GDM. The study also demonstrated that the number of abnormal OGTT values obtained during the GDM diagnosis influenced maternal outcomes (hydramnios, severe hyperglycaemia and need for caesarean section) and neonatal outcomes (macrosomia and large for gestational age). Furthermore it was demonstrated that the fasting and the one hour plasma glucose values obtained during diagnostic OGTTs help predict the development of maternal and neonatal complications.