Which physiological change is typical during the first trimester of pregnancy?

Increased maternal blood volume is a key physiological change that occurs during the first trimester of pregnancy. This increase begins early in pregnancy as the body prepares for the growing fetus and the demands it places on the mother's circulatory system. The plasma volume expands significantly, often increasing by about 40-50% by the end of the pregnancy. This physiological adjustment supports the developing placenta and fetus, ensuring adequate nutrient and oxygen delivery while also preparing the mother for the blood loss that might occur during delivery.

During this time, several compensatory mechanisms are also at play, which can affect other physiological parameters. For example, despite the increased blood volume, many women may experience lower blood pressure due to vasodilation, which is a result of hormones like progesterone that relax the smooth muscles in the blood vessels. This change, however, is not an independent physiological change but rather a response related to the increased vascular capacity.

Additionally, during the early stages of pregnancy, the heart rate may not necessarily decrease; it often remains relatively stable or may increase slightly due to the increased demand for blood flow. The respiratory rate generally does not increase markedly during the first trimester, but tidal volume often increases, improving oxygen exchange. Thus, while other options reflect various physiological changes, increased