During which trimester does a mother's body begin to produce the hormone relaxin?

The correct answer is the first trimester. During pregnancy, relaxin production begins early on, specifically in the first trimester. This hormone plays a crucial role in preparing the body for childbirth by allowing ligaments to become more flexible and enabling the pelvis to expand. This flexibility is essential for accommodating the growing fetus and preparing the body for labor.

The other options refer to trimesters when relaxin’s influence may continue, but the hormone is first produced in significant amounts during the first trimester. Understanding the timing of relaxin's production helps in recognizing its importance in the physiological changes that occur during pregnancy.