Pregnancy Image - Photo credit Microsoft Women who are pregnant realize the positive benefits of exercise. Exercising during pregnancy can enhance energy level, self-esteem and mood. It can reduce physical discomforts during the pregnancy and provide a speedier recovery after delivery, as well as, a faster return to your previous shape. However, pregnancy affects how women should participate in an exercise program and requires safe modifying routines to reduce the chances of physical injury to themselves and the unborn baby.

There are several physiological changes that women who are pregnant experience:

1. Hormonal Changes. Women who are pregnant have an increased level of the hormones: relaxin, elastin, estrogen and progesterone which soften the connective tissues surrounding the joints. This allows the pelvis to expand to accommodate the baby passing through the pelvic inlet during birth.

2. Cardiovascular and Hemodynamic Changes. Pregnant women experience an increase in the blood volume due to the increase of the hormone progesterone. The heart rate and cardiac output are also elevated at rest. Although these changes do no occur simultaneously, they do affect exercise heart rates at different stages of pregnancy.

3. Respiratory Changes. Pregnant women tend to breathe deeper but not faster to meet the increase oxygen requirements due to the pregnancy. Mild to moderate levels of exercise appear to be well tolerated in relations to increases in oxygen consumption.

4. Metabolic Changes. The needs of the growing baby increase the mother's metabolic rate and her core body temperature. Pregnant women are encourage to drink more water before, during and after working out.

5. Endocrine Changes. Pregnant women tend to have lower blood glucose levels due the demands of the fetus. In addition, they tend to burn carbohydrates at a greater rate during exercise.

When pregnant, exercise should be done in a slow and controlled manner. Maintaining strength and tone in the muscles assist lower back support and pushing during delivery. Several safe exercises for pregnant women are walking, swimming or aquatic aerobics, and low-impact aerobic classes.