The Video (Telugu) reminds viewers that Abhimanyu and Prahlada had acquired Bhakthi transmitted by intelligent oral suggestions which after birth gave prenatal and primordial connection to natural tendencies which may or may not have contained mantras or instructions as part of them.
Sounds like an Operant conditioning method of modern behavioral science to induce deep rooted desired behavior that can be carried forward as Vaasanas. The unborn's character can be modeled by design or intent.
It is well known that human personality is influenced by heredity and early life growing environment. In this case it appears heredity and the earliest uterine fetal development environment can play a powerful role for good character and virtuous behavior modeling.
Have there been other such incidences known in other Puranas or history or even folklore? Pregnant mothers are generally advised to keep cheerful but apart from that have there been systematic attempts to instill affinities by tutoring/ mentoring influence like those administered by Arjuna and Narada before birth?
Thanks in advance for references to similar or other anecdotes. If there is more interest I could attempt to put the Video into English.