Hello Kalindi
There is a samskar called Garbhadhan Samskar and during each month the mother can chant a mantra.
First month , one letter mantra
second month 2 letter mantra and so on
But you should get the mantra from a learned man who had already practiced this mantra and reached the higher levels of his consciousness .
We can call him The Guru. If you ask from where you will get a guru,
if your wish to have a guru is so intense the guru will come to you .
May you have that blessing from your Kula devatha to meet a Guru
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Sadhakan