Those who said: if he divorces her three times while she is pregnant she is not lawful to him until she marries another husband

Ibrahim, Amir (al-Sha'bi), Mus'ab bin Sa'd, Abu Malik and Abdullah bin Shaddad said: If a man gives his wife three divorces while she is pregnant, she is not lawful for him until she marries another man.

Something similar is reported from Amir (al-Sha'bi).

Mus'ab bin Sa'd, Abu Malik and Abdullah bin Shaddad said: If a man divorces his wife three times while she is pregnant, she is not lawful for him until she marries another husband.