Final answer:
During the second trimester of pregnancy, normal cardiovascular system changes include increased blood volume, moderately elevated pulse and blood pressure, and the possibility of developing varicose veins or hemorrhoids due to compression of pelvic blood vessels.
Step-by-step explanation:
During the second trimester of pregnancy, several cardiovascular system changes occur that are considered normal. The blood volume increases by approximately 1-2 liters, or 30 percent more than its preconception volume. This increased blood volume helps meet the demands of fetal nourishment and waste removal. Additionally, both the pulse and blood pressure moderately rise during pregnancy. The growing uterus also compresses pelvic blood vessels, which can lead to the development of varicose veins or hemorrhoids.