Causes of Low Blood Pressure During Pregnancy

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Low blood pressure is also called hypotension. Some symptoms of hypotension include dizziness, fainting and fatigue. Severe hypotension in pregnancy indicates a more life-threatening condition, like a heart condition. Typically, pregnant women have temporary bouts of hypotension that are due to normal body changes. The Mayo Clinic points out that hypotension is treatable, but understanding the cause is important in preventing complications.

Blood Vessel Expansion

Pregnant women can drop as much as five to 10 points on systolic pressure or 10 to 15 points on diastolic pressure until they give birth, explains the Mayo Clinic. Early in pregnancy, the blood vessels expand in preparation for providing for the baby. The blood volume has not yet caught up, so the heart has to work harder to get the blood circulated. This can cause blood pressure to lower.

Supine Hypotension

Supine hypotension is a common cause of suddenly low blood pressure. When a pregnant woman lies down, the uterus puts pressure on major blood vessels in the body, the aorta and vena cava, states the American Pregnancy Association. This can slow the circulation of blood. Some women report feeling a sense of suffocation or anxiety when this occurs. Resting on the side or avoiding lying on the back can prevent this type of hypotension.

Postural Hypotension

Postural hypotension happens to just about everyone at some point. Pregnant women are more likely to experience it due to the greater blood volume in the body. This type of blood pressure drop occurs when a woman rises quickly from a resting position, such as sitting or squatting. The gravity forces the blood to work harder to circulate throughout the body. Taking more time to stand or get out of bed can reduce postural hypotension.


Nutritional deficiencies, such as vitamin B12 and folic acid, can cause anemia, which, in turn, causes low blood pressure, states the American Heart Association. An insufficient level of hydration can also create a deficiency in the body that slows blood circulation. Women should take prenatal vitamins during pregnancy to combat such nutritional deficiencies.