I would say yes but first you need to fix the problem of navicular.
Im one of those people who know that it can be cured with proper hoof care. And no its not hereditary so she not going to pass it on to the foal.
I say you can because I have seen many horse freed from navicular. My mare being one of them and guess what she's been one year and eight months with no signs of navicular and guess what? She's 10 months pregnant and she hasn't had one issue during her whole pregnancy.
Don't breed the horse if it still has navicular because yes the added weight will cause more pain but Im not say you eventually can't if you know what to do