The following is the AMJA declaration regarding your question:

General belonging to Judaism or Christianity is what is required in women to be considered from the People of the Book. Marrying the chaste women of the People of the Book is valid with karaahah (it is disliked). However, this kind of marriage is risky, especially when considering the future of children involved. Furthermore, the resolution clarifies that wives from the People of the Book possess the right to practice their religious rituals, and the right to custody of her child until the age of seven, except in a case where this is deemed to cause harm to the creed of the child.