Blood Circulation & Pregnancy

During pregnancy, your body undergoes many changes, and changes to your circulatory system are no exception. Your maternal body adapts to the needs of your baby, since your blood provides all of the nutrients and oxygen your baby will need throughout the pregnancy. Sometimes the changing circulatory system may cause discomfort or complications for you during the pregnancy, but things usually return to normal shortly after the birth of your baby.

Fetal and Maternal Circulation

The presence of your fetus has a huge impact on your circulation during pregnancy. All of the your blood circulates through the placenta, which is attached to the inside wall of your uterus. Oxygenated blood enters your placenta from your arteries and is sent via the umbilical cord vein to your baby. The fetus extracts the nutrients and oxygen it needs from your blood and then sends the deoxygenated blood back to your placenta through the two umbilical arteries in the umbilical cord. This deoxygenated blood then circulates back into your cardiovascular system and is transported via your veins back to your lungs for oxygenation.

Maternal Changes

Doctor examining pregnant woman

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During pregnancy, your total cardiac output and blood volume increases 30 to 50 percent, according to the Merck Manuals. The peak occurs around week 24 and then starts dropping at about week 30 of pregnancy. When labor begins, these things ratchet up again and then drop quickly during delivery when blood is lost as a result of birth. Your heart rate rises to about 90 beats per minute. Blood pressure typically drops in the second trimester, but rises again during the third trimester. The composition of your blood also changes, creating a higher ratio of plasma to red blood cells than in non-pregnant women.


Some of the changes in your blood circulation during pregnancy may cause you discomfort. Swelling is common, especially in the legs and feet, due to the increased blood volume and the pressure on your veins in these lower extremities. Lower blood pressure and higher blood volume may also contribute to fatigue and headaches during pregnancy. You may also develop hemorrhoids as a consequence of restricted blood flow to the lower half of your body.


Doctor examining pregnant woman

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If your circulatory system does not operate properly during pregnancy, complications can result. Intrauterine growth restriction, or IUGR, is a condition in which the fetus does not grow properly and can be a result of poor circulation or defects in your placenta or umbilical cord. Health threats to you may include pre-eclampsia, a dangerous rise in blood pressure accompanied by protein in your urine. You may also develop anemia as increased red blood cells use up available stores. Maintaining regular prenatal care will help you remain healthy throughout your pregnancy.

Recommendations, the virtual OB-GYN office, recommends sleeping on your left side during pregnancy to avoid obstructing yourvena cava, the vein that controls blood flow from your lower body back up to your heart. Since standing and sitting can cause more buildup of blood in your lower extremities, avoid prolonged standing and sit with your feet up.