Also, there’s the possibility of some parents being less in a rush to potty-train the kids if they think these might be the only kids they might ever have. There have been some real-life trends of parents finding it more convenient to potty-train kids later, see e.g. here. This is the way I treated the idea in Childhood’s End, an earlier flash-fiction story of mine that is based around the same concept, though there it was about the last pre-plague generations.
Also, there’s the possibility of some parents being less in a rush to potty-train the kids if they think these might be the only kids they might ever have. There have been some real-life trends of parents finding it more convenient to potty-train kids later, see e.g. here. This is the way I treated the idea in Childhood’s End, an earlier flash-fiction story of mine that is based around the same concept, though there it was about the last pre-plague generations.