A grade 3 placenta is marked by the 39th week of pregnancy up to the due date, significant shadowing on the ultrasound and complete indentations of the chorionic plate known as cotyledons, according to LearningRadiology.com. A premature grade 3 placenta may be caused by smoking, hypertension and diabetes.
A grade 3 placenta is normal at 40 weeks. However, calcifications early in the pregnancy may indicate the placenta is maturing too rapidly, notes BabyMed. Doctors who note these calcifications may watch the baby's growth more carefully to ensure the fetus receives proper nutrition.
When a grade 3 placenta occurs before the 39th week of pregnancy, it may be a sign of placental insufficiency, states Radiopaedia.org. Placental insufficiency denotes a lack of nutrition and oxygen in the fetus. This type of insufficiency is caused by a lack of blood flow from the mother, improper blood flow within the fetus or vascular thrombosis. The major cause of placental insufficiency in a grade 3 placenta is drug use, but it may be caused by high blood pressure, smoking and other underlying health conditions present in the mother.
A mature placenta at full term is divided into leaf-like sections known as lobules or cotyledons, according to American Family Physician. The placenta should look maroon on the maternal side, with shiny gray colors underneath where the baby is located.