The question of how exercise affects the third trimester of pregnancy is constantly coming up for pregnant women. There have been several thoughts in the past as to why pregnant women should not exercise, especially in later stages of pregnancy. Some of these thoughts include that it could increase the risk of preterm labor or divert blood flow to working muscles and reducing placental circulation (Hoffman, Schramm, Stockbauer, 1996). Exercise is good for every individual, including pregnant women, as long as women are careful during exercise.
Moderate intensity physical activity, at least three times a week, is defined as exercise during pregnancy (Bo, Haakstad, Henriksen, ...view middle of the document...
Pregnancy increases cardiac output in a woman (Bader, Bader, Braunwald, Rose, 1955). Exercise also increases heart rate and stroke volume, which increases cardiac output (Katch, Katch, & McArdle, 2011); therefore, pregnant women have an increased cardiac output. The increase in stroke volume is caused by an increase in plasma volume (Abdulla & Abdulla, 2004). During exercise blood is shunted from organs to the muscle (Abdulla &Abdulla, 2004). Some increased concern is that blood flow is being shunted from the organs, such as the uterus, to supply the muscles (Abdulla & Abdulla, 2004). The decrease in uterine blood flow during exercise does not appear to harm the fetus, because there is a preferential shift of blood flow to the placenta and also increased oxygen extraction (Johnson & Morris, 2005). Increased peripheral pooling can be caused by prolonged standing (Abdulla & Abdulla, 2004); therefore, it is important for pregnant women to be aware of their body position.
Oxygen and Energy Demand
Oxygen consumption is somewhat elevated during pregnancy, as well (Bader, Bader, Braunwald, Rose, 1955). During exercise, women who are pregnant have a greater increase in respiratory frequency and oxygen consumption, in order to meet the greater oxygen demand that they have (Abdulla & Abdulla, 2004). In addition to pregnant women having a greater oxygen demand, they also have a higher demand for energy (Abdulla & Abdulla, 2004). Exercise increases the already higher need for energy in women who are pregnant (Abdulla & Abdulla, 2004). As long as the women follow the appropriate instructions in regards to exercise and do not over exert themselves, then the increased oxygen and energy demand is met (Abdulla & Abdulla, 2004).
Women who participate in heavy exercise during pregnancy reduce the risk of delivering prematurely (Hatch, Levin, Shu, Susser, 1998). In addition to reducing the risk of early delivery, women who participate in heavy exercise deliver quicker (Hatch et al., 1998). Spending less time in labor makes the birthing process less exhausting for women. In comparing low to moderate exercise to heavy exercise, low to moderate exercise showed no difference in the delivery time (Hatch et al., 1998). Heavy exercise is defined as higher than 1000 kcal per week (Hatch et al., 1998). The main differences in the women that exercised and did not exercise during pregnancy were smoking habits, education, and income (Hatch et al., 1998).
It is important for a woman who is pregnant to see a physician before she begins an exercise regimen (Abdulla & Abdulla, 2004). Each woman should have a regimen that is structured to her needs, goals, physical condition, and overall general health (Abdulla & Abdulla, 2004). It is recommend that...