At what gestational age does the placenta typically start to break down?

The placenta typically starts to break down around 40 weeks of gestation, coinciding with the time when the body prepares for labor and delivery. This breakdown is known as placental senescence, which is a normal part of the pregnancy process as it reaches term. The deterioration of the placenta is crucial, as it signifies that the fetus is prepared to transition to life outside the womb.

Around this time, hormonal changes occur that are essential for initiating labor, and the placenta's functions begin to decline. In contrast, the later options would indicate a prolonged gestation period that is generally considered abnormal, as most pregnancies are expected to conclude by 42 weeks. Therefore, 40 weeks is the most appropriate answer, reflecting the typical timeframe for the placental changes to begin prior to birth.