Low Blood Pressure and Pregnancy

Question:

I am pregnant and have low blood pressure. Will low blood pressure affect pregnancy?

Answer:

When you’re pregnant, your cardiovascular system undergoes dramatic changes to accommodate the baby: heart rate increases so that the heart pumps more blood per minute, and the amount of blood in your body expands by 40 to 45 per cent; that results in a lower blood pressure than normal.

During a normal pregnancy, the blood pressure decreases in the beginning, reaching its lowest point at around 16 to 18 weeks. It then begins to rise, returning to its regular level by the end of pregnancy.

Most of the time, your cardiovascular and nervous systems are able to adjust to the lowered blood pressure, but occasionally they do not, which can leave you feeling lightheaded or a bit dizzy.

If you actually faint, it could be a sign that something is wrong, and you should call your gynae.

Lying on your left side will maximise the blood flow to your heart – and thus to your brain. It will likely keep you from actually fainting and may relieve the sensation of lightheadedness altogether.

Here are some of the most common causes of lightheadedness during pregnancy and some advice on how to avoid them:

Standing up too fast

When you sit, blood pools in your lower extremities (your feet and lower legs). If your body is not able to adjust when you stand up, not enough blood returns to your heart from your legs. As a result, your blood pressure drops quickly, which can leave you feeling faint. This can happen to people who are not pregnant as well.

When you need to sit in one place for a long time, move your legs frequently to promote circulation. Wearing support stockings can also help circulation in the lower half of your body.

Compressed inferior vena cava

Lying on your back in your second and third trimesters, your growing uterus can slow the circulation in your legs by compressing the inferior vena cava (the large vein that returns blood from the lower half of the body to the heart) and the pelvic veins.

Lying flat on your back can make this problem worse. In fact, about eight per cent of pregnant women in their second and third trimesters develop a condition called supine hypotensive syndrome: When they lie on their back, their heart rate increases, their blood pressure drops, and they feel anxious, lightheaded, and nauseated until they shift their position.