Low Lying Placenta at 28 weeks

Hey Ladies!

I posted a while back about having marginal placenta previa at my 18 week ultrasound.  Well I went for a follow up ultrasound at 28 weeks and they said that my placenta is still low lying.  The OB told me that it is 1.3 cm away from the cervix and that my family doctor actually sent me too early so he wants me to go back around 35-36 weeks to see if it has migrated upwards anymore.  He said 80% chance it will and it only needs to move 7mm.  Has anyone else had a low lying placenta that resolved itself after 28 weeks?  And is it true that it only has to be 2cm away from the cerivcal opening to delivery naturally?

Thanks!