Which of the following changes in hormone levels is normal during pregnancy?

During pregnancy, there are significant hormonal changes that support the health of both the mother and the developing fetus. One of the key changes is the increased production of estrogen. Estrogen plays a vital role in various aspects of pregnancy, including the development of the placenta, regulation of maternal blood flow, and preparation of the body for labor and lactation.

Estrogen levels rise substantially throughout pregnancy, primarily due to the placenta as it becomes the primary source of this hormone. This elevation helps to maintain the pregnancy and promotes fetal growth. It also contributes to the development of secondary sexual characteristics and enhances uterine muscle growth, among other functions.

The other options reflect changes that do not align with typical hormonal shifts observed during pregnancy. Cortisol levels generally increase to help manage stress and support metabolism, progesterone levels rise to maintain the uterine lining, and hormone production does adjust significantly rather than remain unchanged. Therefore, the increase in estrogen is a hallmark of normal hormonal adaptation during pregnancy, making this answer the most fitting.