In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Responding to the question, Sheikh M. S. Al-Munajjid, a prominent Saudi Muslim lecturer and author, states:
It is permissible for a man to lead his wife in prayer, and the woman should stand behind the man.
It is also indicated by the report narrated from Anas ibn Malik, that the Messenger of Allah (peace and blessingsbe upon him) led him and his mother or maternal aunt in prayer. He said, “He made me stand to his right and he made the woman stand behind us.” (Muslim)
“If there is a woman praying with the imam, he should make her stand behind him.”
Ibn Rushd al-Hafeed said:
“There is no dispute concerning the fact that a lone woman may pray behind the imam and that if there is also a man present, the man should pray beside the imam and the woman should pray behind him.” (Ahkam al-Imamah wal-Itimam by Al-Munif, 319-320)
Almighty Allah knows best.