The Ruling on Divorcing a Pregnant Woman

Question :

I divorced my wife and five months after I had married another, I became aware that a daughter had been born to me. Is the divorce permissible or not, since I did not know that she was pregnant? And is it permissible for me to take her back or not? When I visited my daughter, the divorced wife's father refused to accept a fixed sum of money which I pay every month for the daughter. Bearing in mind that every month, when I visit her, I bring only clothes for her, is there any responsibility upon me or any sin? Advise us, and may Allah bless you.

Question :

The divorce of a pregnant woman is valid and it is counted, because it is a divorce according to the Sunnah, as opposed to divorcing a menstruating woman, which is an innovation. Similarly, divorcing a woman who is not pregnant, if her husband has had sexual intercourse with her during that period of purity, then divorced her and it is not clear if she was pregnant, this is an innovation. In any case, this divorce is counted and it is valid. If the divorce is the first or second, it is permissible for him to take her back, if she accepts it and with a new contract and a new dowry. If it is the third, then she is not permissible for you until after she has married another.

You must spend on your wife for the duration of her pregnancy, and if it has passed, and you did not spend on her until the child began breast-feeding, the requirement of that spending is lifted from you. As for spending upon your daughter, it is obligatory for you. But if during the pregnancy, the spending was taken care of by the mother's father, then the responsibility is lifted from you. And if you give them a sum which you have agreed upon, without it being fixed, there is no objection. But if you disagree regarding the fixing of the sum, you may raise the matter with the Judge of the town in order to determine the rightful sustenance for this child every month. And Allah knows best.

Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 6 Pages 30-31