From him, from Safwan, who said:
I asked Abu Al-Hasan عليه السلام about a pregnant woman who sees blood for three or four days. Should she pray? Imam عليه السلام said: "She should refrain from prayer."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 410