Reference: Fataawa ash-Shaykh al-‘Allaamah Muhammad Naasiruddeen al-Albaanee fil-Madeenah wal-Imaaraat – Page 237
Fataawa al-Imaaraat – Page 36
Question: Is it permissible for a pregnant woman to pray sitting down/seated, if she fears miscarrying [her unborn child]?
Response: Yes, it is permissible.