What is the primary maternal organ responsible for producing renin during pregnancy?

During pregnancy, the kidneys play a crucial role in maintaining fluid balance and regulating blood pressure due to the significant hemodynamic changes that occur. The primary site of renin production in the body is the juxtaglomerular cells of the kidneys. Renin is an enzyme that is essential for the renin-angiotensin-aldosterone system (RAAS), which helps to manage blood volume and pressure, crucial factors that can affect maternal and fetal health.

The placenta, liver, and lungs do have various functions during pregnancy, but they are not the primary producers of renin. The placenta is involved in hormonal production and nutrient exchange but does not specifically produce renin. The liver plays roles in metabolism and detoxification but is not directly engaged in renin production. The lungs are crucial for gas exchange but are not involved in the synthesis of renin. Therefore, the kidneys are the correct answer, as they are the primary maternal organ responsible for producing renin during pregnancy.