Meditation or practicing technique has benefits of prenatal elaboration?
When one make positive vibration (Kamma) this effect people around you. This is like the hanky effect. Say you wrap a perfumed flower (good person) then the hanky (another person) then the hanky will also smell good. If you warp dried fish (bad person) then the hanky will smell bad. Likewise if the mother is creating good vibrations then the child maybe influenced.

Also if the mother has been good even before conception then this would attract a good child with also more merit.