Many doctors don't want you eating salt as it can lead to fluid retention. However, you do actually need salt as you end up producing 40% more blood than pre-pregnancy. It's just that it's added to everything anyway, so it's about keeping an eye on it, rather than stopping eating salt all together (we'd die if we didn't consume any salt at all). So just keep it in moderation and balance it with fluids.

I'd be concentrating more on getting high enough levels of protein and calcium.