If you watch old movies, you know that fainting was a tell-tale sign of pregnancy for the heroines of yesterday. When you're pregnant, you may feel woozy or dizzy for the first time in your life, especially if you stand up too quickly or stay on your feet too long. Many factors contribute to dizziness during pregnancy; most of the time, dizziness in pregnancy does not have a serious cause. However, severe dizziness or dizziness that recurs may need evaluation; several serious medical conditions cause cause dizziness during pregnancy.
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Pregnancy causes changes in your blood vessels and blood volume that can contribute to dizziness. Your blood volume increases by 40 to 45 percent, according to Baby Center, to supply your baby with nutrition through the placenta. At the same time, blood vessels widen and relax to carry the extra fluid load. Your blood pressure lowers as a result, reaching a low point in the middle of pregnancy. If you get up too fast or stand too long, blood that pools in your legs doesn't have time to reach your heart and brain quickly and you may feel dizzy. Get up slowly from a sitting position, especially if your legs have been hanging down and don't stand in one place for long periods. Walking keeps blood circulating and prevents pools in the lower extremities.
Vena Cava Compression
Lying on your back in the second half of your pregnancy, when the uterus grows larger, can compress the superior vena cava, a large blood vessel that carries blood from the lower half of the body, slowing blood return and causing lightheadedness from decreased blood supply to the heart and brain. Around 8 percent of women develop supine hypotensive syndrome, which causes lightheadedness, anxiety and nausea when lying on their backs, Baby Center states. (Lie on your left side to decrease vena cava compression and maintain the best blood flow to your upper body as well as to the baby.
Pregnant women can develop iron-deficiency anemia, which can cause dizziness from lack of oxygen. If you have anemia, you have low iron stores. Since iron helps form red blood cells and carries oxygen, you may feel like your heart is pounding and feel lightheaded and short of breath. Anemia develops in pregnancy more frequently than at other times because you have an increased blood volume and need more red blood cells. Getting 27 mg of iron daily helps prevent anemia in pregnancy. Eating foods high in vitamin C along with iron-rich food can increase iron absorption.
Dizziness can occur from serious blood loss in ectopic pregnancy. Ectopic pregnancies grow outside the uterus, usually in the fallopian tube. Because the tube doesn't expand enough to hold the growing fetus, it ruptures, causing potentially large and dangerous amounts of blood loss. Ectopic pregnancy, which affects between one in 40 to one in 100 pregnancies, according to MedlinePlus, generally develops in the first 12 weeks of pregnancy; abdominal pain may also occur. Late in pregnancy, placental abruption, a separation of the placenta from the uterine wall, or placenta previa, a low-lying placenta, can cause blood loss that leads to dizziness. Seek immediate medical attention if you experience vaginal bleeding, extreme dizziness or passing out during pregnancy.