Dear Practo user,
Placenta is afterbirth i.e. thing which comes out after delivery. Placenta is communication between baby and mother (through umbilical cord) and has several roles in nutrition, excretion of waste products etc. It can be located anywhere over the inner wall of the uterus. Anterior means front. This location is normal for placenta. Grading indicates maturity of the placenta. Grade 2 at 20 weeks of gestation is normal. As per the information given, at present, there is no risk for the baby as far as placenta is concerned.