Increased Blood Volume in pregnancy


Your blood system changes dramatically during pregnancy. Your blood volume increases to about 50% more than before you became pregnant. However this amount varies from woman to woman. This is important as it is designed to meet the demands of your growing uterus. This increase does not include the blood in the embryo whose circulation is separate. More blood in your system protects you and your baby from harm when you lie down or stand up. The increase is also a safeguard when you lose blood during labor and delivery. The blood volume increase begins during the first trimester and the largest increase happens during the middle trimester and the increase tends to slow down in the final trimester. Red blood cells and plasma (composition of blood) both increase during pregnancy; plasma increases more. The increase in red blood cells increases your body's demand for iron. The increase in plasma can cause anemia. If you are anemic, especially during pregnancy, you may feel tired, fatigue easily or experience a general feeling of ill health.