What is to be done if, after marriage, a groom discovers that his bride is pregnant by her ex-husband?

Scholars have unanimously agreed that the waiting period (iddah) of a pregnant woman ends with her giving birth. It is not permissible to marry a woman who is in her iddah. If the marriage contract was invalid, then if no intercourse occurred, it is permissible for the husband to conclude a new contract with her after the iddah ends. If intercourse did occur, the Shafi'is, Hanafis, and Hanbalis have held that it is permissible for him to marry her with a new contract after the iddah. However, a group of scholars believes that she becomes permanently forbidden to him. Accordingly, the marriage contract of the aforementioned husband is invalid. If no intercourse occurred, there is no impediment to a new contract after she gives birth. But if intercourse did occur, it is more cautious for him to separate from her and seek another wife.