Is there any Shar’i (Islamic legal) evidence for the recommendation of reciting Surat Maryam to ease childbirth, and Surat Yusuf to improve the baby's beauty for a pregnant woman?

There is no Shar'i (Islamic legal) evidence to prove that a pregnant woman's recitation of specific Surahs from the Qur'an affects the intelligence or beauty of the fetus. Anyone who claims otherwise exceeds their bounds. What circulates in some forums about non-methodological experiences cannot be relied upon. The entire Qur'an is goodness and blessing, but that does not mean we attribute every desired matter to it. Allah Almighty says: (It is He Who fashions you in the wombs as He wills. There is no deity except Him, the Almighty, the All-Wise). There is no harm in a pregnant woman habitually reading and listening to the Qur'an for the fetus to be affected by external sounds. If the sound is that of a Qur'an reciter, it is hoped that there will be goodness and blessing in it for the fetus, without specifying the type of this benefit.