My placenta was anterior too with during my first pregnancy. Or should I say DD's placenta, as it was really hers, not mine.
Apparently, babies have a tendency to want to "look at their food source", so if your placenta is at the front, baby has a higher chance of being posterior.
Having said that, DD was LOL (Left occiput lateral, which means looking to the side) for most of my late pregnancy. I was a little worried about her turning posterior, so I did follow some OFP (Optimal fetal positioning) techniques in the last couple of weeks. She was born relatively easily and completely naturally in the water after only 4 hours of active labour.
This time placenta is posterior. Who knows, I might end up with a posterior bub this time around, just to be different.....

Saša