Final answer:
Maternal blood pressure moderately rises during pregnancy due to an increased blood volume necessary for fetal development, along with hormonal changes and physical compression of pelvic blood vessels by the growing uterus.
Step-by-step explanation:
During pregnancy, there are significant circulatory system changes that impact maternal blood pressure (BP). Blood volume increases by approximately 30 percent, or 1-2 liters, by the time of childbirth, which is necessary to support fetal nourishment and waste removal. As a consequence of the increased blood volume, there is a moderate rise in both pulse and blood pressure. However, as the uterus grows, it can compress the pelvic blood vessels, which can obstruct venous return from the legs and pelvic region. This pressure can lead to the development of varicose veins or hemorrhoids. Additionally, hormone levels such as thyrotropin and ACTH rise, which can influence metabolic rate and contribute to the maternal BP changes. While pregnancy weight gain and increased metabolism all impact the circulatory system, these changes are a normal part of the pregnancy process to accommodate the needs of the developing fetus.