During which period of pregnancy does maternal blood pressure typically decrease the most?

During the second trimester of pregnancy, maternal blood pressure typically decreases the most due to several physiological changes occurring in the body. As the pregnancy progresses, there is an increase in blood volume and changes in the vascular system, including vasodilation, which lowers peripheral vascular resistance. This is particularly pronounced in the second trimester as the body adapts to the growing fetus and the increased demand for blood flow.

Additionally, during this period, the placenta develops fully, contributing to the production of hormones that influence vascular tone and blood flow. As a result, many women experience a decrease in both systolic and diastolic blood pressure during this stage, often leading to a peak drop around the midpoint of pregnancy.

Blood pressure typically stabilizes or may rise again during the third trimester as the growing fetus exerts pressure on the pelvic vessels and the mother's body adjusts to increased circulatory demands and hormonal changes. The dynamics during labor and delivery also involve complex responses that can affect blood pressure differently, but the most significant decrease before labor is noted during the second trimester.