I couldn't tell whether it was a result of the natural progression of the games, or a change from the updates. I'm running 5 families and it is much more difficult to have children. In my first two generations, I never saw them go through the baby making ritual and then walk away with nothing. Now, I see it fairly frequently. I've run the doctor diagnostic, on some there is a message that they need baby boost and I provide it to the parent that needed it, but the couple remained sterile.

In other families, there was no indication that either parent needed baby boost but they couldn't produce additional children.