The placenta is incapable of releasing metabolic products.
Placenta accreta, when the placenta implants too deeply, all the way to the actual muscle of uterine wall (without penetrating it)Placenta praevia, when the placement of the placenta is too close to or blocks the cervixPlacental abruption, premature detachment of the placentaPlacentitis, inflammation of the placenta, such as by TORCH infections
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation

