A mature placenta, according to the Archives of Disease in Childhood Fetal & Neonatal Edition, occurs when placenta looks older than it should be in comparison to the length of the pregnancy. When this happens, the placenta is aging prematurely or at an accelerated pace.
Dr. Nicholas Fogelson from HealthTap goes on to explain that the danger of mature placenta is that it delivers less blood to the infant, especially if it occurs earlier in the pregnancy. MedlinePlus further describes the dangers of this insufficiency. For example, less blood supply to the baby results in a baby who does not grow as well and undergoes fetal stress. This can have a multitude of causes, such as a mother who is diabetic, smokes, is past her due date or suffers from high blood pressure.
Women World points out that mature placenta can come in conjunction with a calcified placenta, which has calcium deposits on the placenta. This is caused by hypertension, diabetes and kidney problems. If the pregnancy is in the 37th week when the calcified placenta is detected, the baby just needs to be monitored. A calcified and mature placenta detected before that time might need medical intervention because the baby is not getting all the nutrients it needs.