What are the best du'as to make during pregnancy ? Is the du'a from 3:35 a good du'a to say ? "Rabbi, indeed I have pledged to You what is in my womb, consecrated [for Your service], so accept this from me. Indeed, You are the Hearing, the Knowing"

There is no dua specific to pregnancy established in the authentic Sunnah, so ask Allah in general for her safety and for a righteous, upright child, for the mother's dua for her child is answered. That ayah is the vow of the wife of Imran, and the scholars (like Alshawkani) state that dedicating a child in that way was of their sharia and is not valid in ours, so do not take it as a vow. Say dua rabbi hab li min ladunka dhurriyyatan Salihah (O, Allah bestow upon me pious children).