My wife and I are planning to have our first baby soon and I’ve read that it’s good for us to read Quran to the baby while they are in the stomach.
I’ve read some pretty specific recommendations about what to read in some books (e.g. recite Surah Maryam daily, recite Surah Yusuf 40 times and blow on apple and eat it … etc), but there doesn’t seem to be any sources to these recommendations, which makes me doubt their authenticity.
So I was wondering if know of a list which details the surahs to read during pregnancy? Or is there no specific recommendation?

There are many recommendations for a pregnant woman.
I wouldn’t follow anything that isn’t sourced.
But there is no loss in reciting the Qur’an in general.

After daily prayers, recite Surat al-Kawthar (108), Surat al-Qadr (97) and the long Ŝalawāt with the hand on the stomach:

أَللٌّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ فَرَجَهُمْ وَ أَهْلِكْ عَدُوَّهُمْ مِنَ الْجِنِّ وَ الإِِنْسِ مِنَ الأََوَّلِينَ وَ الآخِرِينَ.

“O Allāh (SwT)! Bless Muĥammad and the family of Muĥammad, and hasten their release from suffering, and destroy their enemy, and curse their enemies from among the jinn and humankind from the beginning to the end (of time).