Pregnancies affected by both pregestational and gestational diabetes mellitus carry an increased risk of adverse maternal and neonatal outcomes. While the risks associated with diabetes in pregnancy have been well documented and span across all trimesters, maternal and neonatal morbidity have been associated with select third-trimester complications. Further, modifiable risk factors have been identified that can help improve pregnancy outcomes. This review aims to examine the relationship between select third-trimester complications (large for gestational age, intrauterine fetal demise, hypertensive disorders of pregnancy, preterm birth, perineal lacerations, shoulder dystocia, and cesarean delivery) and the aforementioned modifiable risk factors, specifically glycemic control, blood pressure control, and gestational weight gain. It also highlights how early optimization of these modifiable risk factors can reduce adverse maternal, fetal, and neonatal outcomes.