well , since you told that the low lying placenta is just covering the internal os and grade 1 maturity it means that it is a placenta with some part of it extending to lower part of uterus while some part is in the upper pole of uterus ,usually placentas of this sort will become normal over period of time. if they wont tend to regress to upper pole then it is diagnosed as placenta praevia of grade 3 . and it carries the risk of bleeding in third trimester of pregnancy after 30 weeks in some cases . the best advice that i give u is to observe for any fetal distress or maternal distress and any bleeding per vaginum which is mostly painless bleeding. blood transfusion is adviced if their are any bleeding episodes according to ur health assesment . and ceasarian section is advised after 30 weeks on a convenient date after thorough check up of mother and foetus. so at present there is nothing to worry , only observation and regular check up is advised