Changes to the pregnant women’s body begin immediately. Once the fertilized egg is implanted into the uterine wall, the body begins to go through tremendous changes. Various hormones are released that allow the body to get ready to carry a baby. The release of these hormones has a tremendous effect on the cardiovascular and circulatory systems. Most of the changes facilitate an increased efficiency of blood flow and volume to meet the demands of the growing fetus. Some of the changes are listed below.
Cardiovascular Changes During Pregnancy
- Increased volume of the circulatory system
- Increased blood volume
- Increased stroke volume (volume of blood being pumped by the ventricles in on beat)
- Increased cardiac output (volume of blood being pumped in 1 minute)
- Increased heart rate (therefore HR is not a good measure of exercise intensity)
- Decreased blood pressure
These changes can cause lightheadedness, rapid pulse, fatigue, and dizziness when rising from a lying or sitting postures. These symptoms will improve as pregnancy progresses and are often greatly reduced by the 2nd trimester.
The cardiovascular and circulatory changes that are going on in the body will have an effect on exercise performance. Most women will find that they have to reduce their workload as the pregnancy progresses. They will find that working out at a lower level will promote a similar intensity to higher workloads when they were in non-pregnant state. Due to the increased heart rate, women should not use heart rate as a measure of intensity when exercising. Instead, women should use a Rate of Perceived Exertion or RPE chart. Women should stay in a range of a 5-8 on a 10 point scale.
Effect of Cardiovascular Changes on Exercise Performance
- Increased fatigue and reduced stamina
- Heart rate response higher for same workloads compared with non-pregnant state
- Blood pressure drop with positional change (lying to standing) may cause lightheadedness and dizziness
Pregnant women can make cardiovascular gains during pregnancy. Exercise during pregnancy can enhance the changes that occur and further improve cardiovascular efficiency. Women who exercise during pregnancy have a 30-50% increase in blood pumped each heart beat compared to sedentary pregnant women. Capless and Clapp (1989) and Robson et. al. (1989).
Effect of Exercise on Cardiovascular Changes of Pregnancy
- Increased blood volume – plasma volume and red blood count volume increase
- Improved O2 delivery
- Increased blood vessel growth
- Increased circulatory reserve
As a rule, women should not push to extreme levels of fatigue during exercise. This is a time of health and well-being. It is not a time to train for an event or push to new levels of fitness. Be aware of and listen to your body and always seek physicians clearance before beginning a prenatal or postpartum exercise program.If you enjoyed this post, make sure you subscribe to my RSS feed!