What occurs after the withdrawal of progesterone prior to labor?

• A. Uterine contractions begin
• B. Uterine relaxation is maintained
• C. Oxytocin receptors decrease
• D. Mature fetal breathing starts

Answer: (A)

The correct answer reflects the physiological changes that occur in preparation for labor. After progesterone withdrawal, there is a significant increase in uterine excitability, leading to the initiation of uterine contractions. Progesterone plays a crucial role in maintaining uterine quiescence during pregnancy; its levels rising throughout gestation help to keep the uterine muscles relaxed and prevent premature contractions.

When progesterone levels drop, the balance shifts, favoring contractility, and this is typically one of the driving factors that signal the onset of labor. The increase in myometrial responsiveness to other labor-associated hormones, such as oxytocin, further stimulates the onset and progression of labor through rhythmic uterine contractions.

In contrast, uterine relaxation being maintained would contradict the physiological process happening as labor approaches. Oxytocin receptors typically increase as labor nears, which would not be consistent with a decrease in those receptors. Mature fetal breathing is a separate process that occurs independently and is not directly related to the withdrawal of progesterone. Therefore, uterine contractions beginning is the primary and correct response to progesterone withdrawal prior to labor.