Pregnancy puts a strain on your heart and circulatory system. To fuel your developing baby, your blood volume rises by 30 to 50% throughout pregnancy. Each minute, your heart pumps more blood and your heart rate rises. These changes are necessary to provide the body with the oxygen it needs to grow the fetus. The increased blood volume causes your uterus to grow. Your kidneys have to work harder to remove waste from the extra blood and urine produced during pregnancy. All these changes can lead to problems if you have a history of heart disease or hypertension. If you have any of these conditions, make sure that you tell your doctor if you are becoming pregnant. He or she will help you decide what kind of test you should have before you become pregnant. These tests will help identify risks to your health as well as the health of the fetus. There are several ways in which pregnancy affects women with heart disease. If you have angina during pregnancy, there is a risk of having a heart attack or stroke. Pregnant women with heart failure may not be able to handle a rise in temperature or stress properly. They are at risk of developing a condition called decompression sickness (DCS). DCS occurs when bubbles form in your blood due to changes in pressure caused by diving down deep underwater. These bubbles can block arteries leading to your brain and other organs causing death.