Light-headedness, or dizziness, is a very common symptom during pregnancy. Your body is going through some massive changes – weight gain, hormonal shifts, an increase in blood volume and fluctuating blood pressure – that affect your blood flow and can make you feel dizzy. And while light-headedness is not usually caused by anything harmful, it's always a good idea to bring it up with your obstetrician at your next visit – and definitely place a call to your doctor if you actually faint.
Hormones and Low Blood Pressure
The increase in hormones during pregnancy causes a number of symptoms and discomforts for pregnant women, but it can also explain your light-headedness. Pregnancy hormones cause blood vessels to widen so that your growing baby can receive more blood flow, but that also causes the return of that blood supply to your veins to slow down. This causes blood pressure to drop and a reduction in blood flow to the brain, which can leave you feeling dizzy and the room whirling around you.
Low Blood Sugar
Pregnant women need to drink plenty of fluids and eat plenty of snacks throughout the day to keep blood glucose, or sugar, levels from dropping too low. Low blood sugar can cause you to feel nauseous, dizzy and light-headed. Your metabolism changes during pregnancy, and blood sugar can drop as a result of this, says the American Pregnancy Association.
Pressure on the Blood Vessels
Your growing belly adds pressure and stress on the blood vessels surrounding the uterus as it expands with the developing fetus. During your second trimester, that growth and pressure on the blood vessels can cause some dizziness. And in the third trimester, lying on your back puts heavy pressure on the vena cava, which is a major vein that helps supply blood to your heart.
Anemia, which is low red blood cell count, is common in pregnancy and causes light-headedness and dizziness. Anemia is most often caused by iron deficiency. When you're anemic, your brain and other organs don't receive enough oxygen due to the low levels of red blood cells, which can cause light-headedness.
Something as simple as standing up too quickly from a seated position can leave you feeling dizzy, as blood that has pooled in your legs and feet hasn't yet had a chance to reach your heart. Feeling anxious or overwhelmed can cause you to hyperventilate, which is a cause of dizziness. Getting overheated from wearing too many layers, taking a hot bath or being outdoors in hot weather can also lower blood pressure and cause dizziness.