High blood pressure is not really a sign of pregnancy. But high blood pressure can develop during pregnancy and is referred to as preeclampsia, toxemia or pregnancy induced hypertension.

If mild symptoms will also include protein in the urine and water retention.

In more severe cases the symptoms can include light sensitivity, strong headaches, blurred vision, breathing problems, nausea, vomiting, abdominal pain and scanty or frequent urination.

The actual cause of preeclampsia is unknown, but the treatment in the hospital involved the intravenous infusion of magnesium salts. Magnesium lowers blood pressure in a manner similar to calcium channel blockers (CCBs). When calcium enters muscles such as blood vessels the calcium causes the muscles to contract. Contraction of blood vessels lead to an increase of blood pressure. CCBs work by keeping calcium from entering the blood vessels so the blood vessels remain relaxed and the blood pressure stays down. Magnesium is antagonistic to calcium and pushes the calcium out of blood vessels causing them to relax.