Given your high-risk pregnancy history and slow fetal growth, any medication changes must be strictly supervised by your obstetrician. To improve placental blood flow and baby's growth, doctors sometimes consider adding L-arginine supplements, DHA (Omega-3 fatty acids), or low-dose aspirin (if appropriate for your medical profile). Additionally, focus on a high-protein diet, staying well-hydrated, and resting on your left side to maximize blood flow to the uterus. Please do not self-medicate; discuss these specific options with your doctor immediately, as close monitoring of the baby's blood flow via Doppler ultrasound is critical at this stage.