Managing high blood pressure is the best way to prevent strokes. A hemorrhagic stroke results from the rupture of a normal blood vessel from blood pressure which is too high.
There are also ischemic strokes caused by a clot or plaque closing a vein. An ischemic stroke is much less traumatic than a hemorrhagic stroke. In an ischemic stroke, the blood is shut off in a small area by a clot or plaque. This type of stroke is generally less destructive than a hemorrhagic stroke.
If your blood pressure is high during your pregnancy, your doctor could prescribe apresoline (a kind of vasodilator) to lower your blood pressure. However, apresoline tends to raise your heart rate, so propranolol is often also prescibed at the same time to lower the heart rate.
Both the apresoline and the propranolol have been available for many years. They are effective, available, safe, and cheap medications for lowering blood pressure during pregancy.