Purity: Burial of a Pregnant Non-Muslim Woman with a Muslim Foetus
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 608:
If a [pregnant] disbelieving woman dies and the baby in her womb has also died, in the event that the father of the child is a Muslim, the woman must be laid on her left side with her back facing qibla so that the front of the baby faces qibla. The same applies, based on recommended precaution, if the spirit (ruh) has not yet entered the foetus.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)