Will I be sinful if I divorce my pregnant wife after I have uttered the oath of divorce to her and then taken her back, while she insists on divorce and has not yet given birth, knowing that I will utter the oath to her during the same period of purity?

If a woman requests a divorce without a Shar'i (Islamically lawful) reason, her action is forbidden (haram). However, if the husband accedes to her request and divorces her while she is pregnant, her divorce is valid and takes effect by the consensus of the scholars. There is no sin upon him for this, because divorcing a pregnant woman is a Sunnah divorce. Nevertheless, the husband is advised to be deliberate in this matter and to use the divine remedy for a wife's 'nushuz' (rebelliousness/disobedience).