On the one hand, children are less central to marriage than they were before. Single parenthood by choice is on the rise, as are deliberately child-free marriages. On the other hand, for many people, children are perhaps the one remaining imperative to get, and stay, married: parenting is one thing they don't think they can do just as easily on their own. So, when couples do opt to have children, they can become almost entirely defined and consumed by the tasks of parenthood. This is something new for marriage because in the past the roles of husband and wife involved more than just child rearing.