What is a likely reason for the decrease in blood pressure during the second trimester of pregnancy?

During the second trimester of pregnancy, a decrease in blood pressure is often observed. This phenomenon can primarily be attributed to changes in hormonal levels that occur during this time. During pregnancy, hormones such as progesterone lead to the relaxation of blood vessel walls, resulting in vasodilation. This relaxation decreases peripheral resistance, which contributes to lower blood pressure.

While it is true that blood volume increases during pregnancy, this generally leads to increased blood pressure if vascular resistance remains constant. In the case of a healthy pregnancy, the combination of rising blood volume and reduced peripheral resistance often results in a net decrease in blood pressure, particularly evident during the second trimester.

The observation that it is normal for blood pressure to decrease regardless of hypertensive status does hold some truth, but the underlying physiological mechanisms—such as hormonal changes leading to vasodilation—are responsible for this normal decrease in blood pressure. Understanding these mechanisms helps clarify why the correct answer centers on hormonal influences that significantly impact vascular resistance and blood pressure during pregnancy.