And sometimes they both change their minds. I know a couple who first decided not to have kids, she had never had them, but he had grown children and was considerably older. He happily let her change her mind later, they adopted and they adapted to the change really well. The main consideration on such a life changing decision, is that it isn't pressure at the risk of losing the marriage. Decisions made under threat are always resented.
All this debate should point out one very important factor for all concerned.
Whether to have or have not children is a Marriage issue.
Everyone here has let this degenerate, a bit. We should not let the lawyers make marriage an adult sex only activity.