Anterior is a good position po for pregnancy and childbirth.
Low lying can be a cause for concern po if hindi sya magresolve. Pwede pa po sya maging high lying habang lumalaki ang tyan nyo, pero wala pong gamot para dito. You can really just hope na umayos sya, and follow your OB's order.
No previa po meaning kahit medyo mababa ang placenta, hindi naman nya natatakpan yung cervix. May dadaanan si baby para maipanganak.
Just follow your ob po and try not to worry too much about it. 20 weeks pa lang naman po kayo, and pwede pa sya mag-move. Ang mahalaga, no previa po :)
Cii Jeng In