Shortening the prayers is a confirmed Sunnah for all travellers, whereas joining the prayers is permissible but is not Sunnah, but it may be Sunnah and recommended if there is some difficulty involved in not doing it.

Shortening the prayers when travelling is a confirmed Sunnah that one should not forsake, according to the consensus of the imams (leading scholars).

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.

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.