Just like many other bodily functions, the heart rate during pregnancy changes for most women. It tends to increase, because more blood is needed, and much of the blood is going to the uterus. With more blood and body mass, the heart has to pump harder to make the blood circulate properly. While this increases somewhat during the first trimester, the heart rate tends to change most during the second trimester. Some of the problems that can occur, especially in unhealthy women or those with existing heart conditions, include rhythm issues and possible heart failure.
The heart rate during pregnancy tends to increase for most women. Some women’s hearts will be able to pump the excess blood without increasing heart rate, but this normally only happens with very fit women and is uncommon. One reason for the increased heart rate is that more blood is being made, so the heart has to pump all the extra blood and it has to send that blood to the uterus.
The changes in a woman's body mass also cause the heart rate during pregnancy to change. She gets larger as a result of the growing child, so the blood must travel to a larger area. Unlike being overweight, which usually has bad health concerns, the health concerns with an increased heart rate tend to be nominal during pregnancy.
More blood will be needed from the moment the baby begins growing within the mother. At the same time, there normally is not a noticeable increase in heart rate during pregnancy until the second trimester. This is because the fetus begins to grow rapidly during the second trimester, facilitating the need for extra blood.
Heart conditions can become a worry during pregnancy, especially because the heart rate during pregnancy normally increases and there is extra stress on the heart. The least worrying condition can be problems with heart rhythm, because this is normal for most women and should not lead to further problems. Heart failure can occur in pregnant women with weaker hearts, because the heart cannot respond optimally to the extra blood.
Women with artificial valves may experience heart infections or may need to use blood thinners so the blood can go through the valve. Those with artificial valves should speak with their healthcare professionals, because adjustments to their medication may be required. At the same time, if the increased heart rate causes or brings out a heart condition, then it increases the chance that the child also will have a heart condition.