It is not dangerous. This is just an option. To sleep, as usual, the location of the placenta does not affect either the development of the baby or the well -being of the mother. Just a more rare option.
The main thing is that there is no presentation when the edge of the placenta closes the entrance to the uterus, but then it can rise over time, we must observe.
And the location on the front wall can make itself felt only by the fact that the mother will later feel the tremors of the child and will feel a little weaker.
Of course, the attachment of the placenta on the posterior wall of the uterus or on the sides is the most optimal, but attachment on the front wall is not a pathology. The most important thing is that the placenta is not located too low, and that there is no presentation.
Sleep as it is comfortable, just, avoid sleeping on your stomach.
Usually sleep. Both of my placenta was located on the front wall of the uterus. This is not presentation. I was a gynecologist, the same doctor watched both pregnancy, never talked about the features of such a placenta arrangement.