welcome to health care magic
Thanks for your query
Normally placenta is attached in the upper part of uterus
far away from the internal os..
You are 5 months pregnant,,and the placenta is nearer to internal os..in due course of time it will grow and cover the internal os..
During the time of labor,the lower segment stretches so bleeding will be more and it will be harmful to you and also baby..
For placenta praevia(low lying placenta) caesarean section
Consult gynecologist for more details..you should follow up regular ultrasound
Hope you understand my suggestion