The placenta is an amazing organ that actually belongs to the baby.
It develops in the uterus during pregnancy. This structure provides oxygen and nutrients to the growing baby and removes waste products from the baby’s blood. The placenta attaches to the wall of the uterus, and the baby’s umbilical cord is attached to it. The placenta is usually attached to the top, side, front or back of the uterus. In rare cases, the placenta might attach in the lower uterine area and cause problems (placenta previa).
Placenta: How it works, what’s normal, by Mayo Clinic Staff
Aging of the Placenta, by Harold Fox
“It has to be admitted that the pathophysiology of prolonged pregnancy has not been fully elucidated. It seems, however, quite clear that any ill effects which may befall the fetus in prolonged gestations can not be attributed to placental insufficiency or senescence. Conclusions: A review of the available evidence indicates that the placenta does not undergo a true aging change during pregnancy.”
In other words: the placenta does NOT age and cause danger to the baby.