If a pregnant woman is able to pray standing up then she has to stand. Then if she becomes unable to stand or it is too difficult for her to stand, then she can sit down while praying.

A person who suffers from urinary incontinence and constant wind should do wudu at the time of each prayer, and pray as much as he likes with that wudu until the time for the next prayer begins.

It is permissible for a sick person to join prayers, so he may join Dhuhr and `Asr, and Maghrib and `Isha’, at the time of the earlier or later prayer, depending on what is easiest for him. Difficulty caused by sickness is one of the excuses which make it permissible to join prayers.