Final answer:
Progesterone significantly inhibits uterine contractions by decreasing myometrial sensitivity to various hormones. The statement is true. A decrease in progesterone levels towards the end of pregnancy allows for labor contractions to begin.
Step-by-step explanation:
The statement that progesterone exerts a powerful inhibitory effect upon uterine contractions by decreasing the sensitivity of the myometrium to estrogen, oxytocin, and prostaglandins is True. Progesterone plays a crucial role in maintaining pregnancy by inhibiting uterine contractions during the first several months of gestation. As pregnancy progresses, the levels of progesterone plateau and eventually decrease, while estrogen levels continue to rise, leading to an increased sensitivity of the myometrium to contractile stimuli. In the late stages of pregnancy, a drop in progesterone levels contributes to the onset of labor by reducing the hormone's calming effect on the uterus, thus allowing for the intensification of uterine contractions, which is facilitated by increased secretion of estrogen and other hormones like oxytocin and prostaglandins.