What is the ruling on a woman in 'iddah leaving her home to visit her sick mother?

It is permissible for a woman observing the iddah (waiting period) due to death or irrevocable divorce to go out during the day to visit her sick mother, provided she returns to sleep in her home. Visiting a sick mother is a legitimate, recognized need (hajah shariyyah). As for a woman who has been revocably divorced, her going out is conditional upon her husband's permission.